DiscoverHistorical Fiction

The U.S. Navy’s On-the-Roof Gang: Volume 1 - Prelude to War


Must read 🏆

A fascinating look at the beginnings of the U.S. Navy’s radio intercept and cryptanalytic program and the men that made it happen.


THE US NAVY'S ON-THE-ROOF GANG: VOLUME I - PRELUDE TO WAR is an historical novel based on the unknown true-life story of the "On-The-Roof Gang," the U.S. Navy's fledgling radio intelligence organization in the years leading up to World War II. It is based on the real life of Harry Kidder, a U.S. Navy radioman who first discovered and deciphered Japanese katakana telegraphic code while stationed in the Philippines in the 1920s, discovering the he was listening to Imperial Japanese Navy (IJN) radio communications. Kidder taught others the nascent art of intercepting IJN communications on the roof of the Main Navy Building in Washington, DC. From 1928 to 1941, 176 Sailors and Marines attended this training and were then stationed as radio intercept operators around the Pacific. These men would become known as the On-The-Roof Gang and were charged with keeping track of the IJN as they prepared for war with the United States. The circumstances of America's entry into World War II hinged on success or failure of the On-The-Roof Gang, and Harry Kidder knew this. On-the-Roof Gang: Prelude to War concludes with the "date which will live in infamy," December 7, 1941.

Matt Zullo’s new book, The U.S. Navy’s On-the-Roof Gang: Volume One – Prelude to War, was a fascinating and well-told story. The characters and events absolutely came alive – no dry-as-dust history lesson here. In fact, I was immediately ready to jump into the rest of the story in Volume Two!

The book truly made for exciting reading seeing the creation of this secret, new unit with the mission of intercepting and analyzing the contents of the Japanese messages. I was amazed at the feat these guys accomplished just in being able to copy, report, and then convert to usable information the code they heard over great distances and under pretty rough conditions (both physically and atmospherically.) They were taking the ‘dits and dahs’ of encrypted Japanese and eventually translating it into English.

I felt the frustration of these men as they struggled to gain support from those in Washington, DC and, sometimes, even at the various places they had established listening stations. I was shocked when the Secretary of State under Hoover, Henry Stimson, shut down the joint code-breaking organization of the U.S. Army and the State Department (leaving the only the Navy’s group in operation) saying “Gentlemen do not read each other’s mail.”

One thing that made the events and history so much more interesting to me were the details that kept anchoring this story to what the world was like during this time. For example, at this time (the 1920s and 30s), telephones were not in every home or office. Households were still using gaslights as not everyone had been able to afford the transition to electric lights as yet. Aircraft carriers were relatively new ships in the fleet.

I appreciated the look inside day-to-day naval operations as well. The author provides a nice and useful key to abbreviations at the end of the book, but there were also little tidbits of information regarding rank, duties, and duty stations worked into the story, too. I learned that there is a universal compartment-marking scheme, a letter-number designation which will tell you where a particular location is on board ship.

I highly recommend this book to readers of non-fiction, historical fiction, World War II buffs, and ham radio enthusiasts. It was engaging, easy-to-read, and totally engrossing. I loved it!

Reviewed by

I love to read and hook up others with books that they might enjoy. I like genre fiction with a weakness for cozies, post-apocalyptic, dystopian, and westerns. My professional background is in law enforcement, fire, water, and environmental education. I have basset hounds and ham radio is a hobby.


THE US NAVY'S ON-THE-ROOF GANG: VOLUME I - PRELUDE TO WAR is an historical novel based on the unknown true-life story of the "On-The-Roof Gang," the U.S. Navy's fledgling radio intelligence organization in the years leading up to World War II. It is based on the real life of Harry Kidder, a U.S. Navy radioman who first discovered and deciphered Japanese katakana telegraphic code while stationed in the Philippines in the 1920s, discovering the he was listening to Imperial Japanese Navy (IJN) radio communications. Kidder taught others the nascent art of intercepting IJN communications on the roof of the Main Navy Building in Washington, DC. From 1928 to 1941, 176 Sailors and Marines attended this training and were then stationed as radio intercept operators around the Pacific. These men would become known as the On-The-Roof Gang and were charged with keeping track of the IJN as they prepared for war with the United States. The circumstances of America's entry into World War II hinged on success or failure of the On-The-Roof Gang, and Harry Kidder knew this. On-the-Roof Gang: Prelude to War concludes with the "date which will live in infamy," December 7, 1941.

Harry Kidder

Saturday, June 7, 1924

Los Baños, Philippines


Harry Kidder was already ten minutes late for watch, but he was dead asleep. The warm sun and early morning breeze from the open window next to his bed did nothing to wake him. Outside, below his second-floor window, shopkeepers were preparing their wares for the day’s customers. Muted conversations in Tagalog echoed up through Harry’s window, but he was completely oblivious to them. Although the volume knob was set to zero, the radio gear on the table next to his bed buzzed with electricity.

Outside, a milk bottle crashed to the ground, finally waking Kidder from his slumber. Looking at the clock next to his radio, he cursed under his breath, hauled himself out of bed, and rushed to shave, shower, and throw on his uniform—the standard-issue long-sleeved chambray shirt and denim bell-bottom dungarees with patch pockets sewn on the front and back. Because of the tropical weather in the western Pacific, Asiatic Fleet commanders permitted Sailors to roll up their sleeves to just above the elbow. A white, Dixie cup hat topped off the uniform. It was this last piece of gear that gave U.S. Navy petty officers their nickname: White Hats.

It took Petty Officer Kidder less than ten minutes to get ready and head out the door. The front gate of Camp Eldridge was only a five-minute walk from his one-bedroom apartment, but that meant he’d still be a half hour late—and his chief was going to kill him.

It was approaching 0800 hours on this particular Saturday morning as Petty Officer Harry Kidder hurried through the mostly quiet streets of Los Baños, his white hat cocked back on his head. Other than the occasional Sailor stumbling home after a night of debauchery and the fishermen preparing for a day on Laguna Lake, the Philippine Islands town was eerily quiet. Beer bottles and discarded wooden skewers from the town’s famed “meat on a stick” littered the dirt roads. The meat was always pork, but the Sailors frequently joked that it was monkey or dog. In actuality, both monkey and dog meat were much more expensive than pork and were considered delicacies in the Philippines.

Harry was almost thirty minutes late for watch and picked up his pace as he neared the main gate to the naval base. When he arrived, he flashed his identification card to the guard then broke into a slow jog toward the low one-story building marked “U.S. Navy COMSTA, Camp Eldridge.” At the door, he quickly rang the buzzer. A disinterested Sailor opened it and Harry rushed in. He hurried through two more doors as he made his way to the operations floor.

As usual, the room was dark, except for the radio dials and the occasional desk lamp dimly illuminating the watch standers’ faces. Because the work that took place in the building was highly classified, the windows were painted on the inside and covered with dark curtains. Just about everyone smoked, so a dull haze hovered in the air, contributing to the subdued lighting. Harry liked it though; it made his work seem more clandestine.

With his headphones on, Radioman Second Class Phillip Johnson sat at his station. As Harry approached, Johnson looked straight at him with his eyes wide as if to warn him of immediate danger. Chief Radioman Bud Karcher stood behind Petty Officer Johnson, facing the door and waiting for Harry to arrive. Karcher looked at his watch, lit cigarette in hand, and grumbled, “Thirty-four minutes late, Kidder.”

“I know, Chief. I’m sorry.”

“You don’t have to apologize to me; it’s Johnson you’ve made stay on watch thirty-four . . . ,” he paused, looking at his watch. “Thirty-five minutes extra.”

“I’m sorry, Johnson.”

Johnson really didn’t mind that much. He actually felt sorry for Harry, knowing that the chief was about to lay into him. He shrugged at Kidder, not wanting to be a part of the tense situation any more than he already was.

“God dammit, Kidder! How many times do we have to do this?”

Recognizing this was a rhetorical question, Kidder kept his mouth shut.

“What is it this time? Late night after a bar fine?” In the Philippines, when Sailors left with bar girls before closing time, they were required to pay the bar owner a fine, allegedly to compensate him for lost income due to the girl’s absence. This was in addition to any payment the girl might want based on services rendered. In all his time in the Philippines, Harry had never once paid a bar fine.

“No, Chief,” Harry responded, embarrassed by the insinuation.

“Don't you like girls, Kidder?” the chief mocked.

His embarrassment growing, Kidder responded, “Uh . . . no . . . that’s not it, Chief.” The truth was that Kidder didn’t have much experience with women, and he wasn’t ever brave enough to pay a bar fine.

“Choir practice after work yesterday?” the chief chided, referring to a euphemism among Sailors in the Philippines who claimed they were going to choir practice, when they were really going drinking. “Get drunk and pass out in a gutter?”

“No, Chief,” Kidder said flatly as he felt the redness in his cheeks growing.

“What, then?”

Finally, Harry sensed an opportunity to explain. “Chief, I was up late with my ham rig. I actually spoke to somebody in Maine last night!” Amateur radio, or Ham radio, was Kidder’s new hobby—his passion, really. Ham radio was a relatively new avocation born out of the rapidly increasing technology of radio communications. Kidder had been fascinated with radio since childhood, and he found like-minded individuals around the globe on the airwaves. Ham radio enthusiasts communicated via international Morse code—a series of dits and dahs transmitted to represent the letters of the alphabet, numbers, and punctuation marks. In this way, it was possible to send a message in Morse code simply by turning a signal on and off in the correct manner to represent the dits and dahs. Each dit-dah combination represented a letter in international Morse code, which was the internationally accepted standard in Continuous Wave (CW) communications. Kidder was obsessed with being a ham operator and had subscribed to a relatively new magazine called QST, which was published by the American Relay League. The magazine instructed readers on how to build and operate their own amateur radio radios and antennas. Because of his Navy job, Harry could copy up to thirty-five words per minute before he ever applied for his amateur radio license, which only required five words per minute for an entry-level license. On the day when he finally received his license, he smiled when he saw he received the call sign he requested: PI 1HK.

Despite the appearance that his frequent tardiness projected, having a job in this high-tech field was exactly what Kidder was hoping for when he joined the navy. And his love for the job spilled over into his personal life. His self-built radio rig and rudimentary dipole antenna worked exceedingly well. Kidder considered himself lucky that his job was so similar to his hobby. At work, he and all other radiomen in the U.S. Navy used Morse code to communicate between ships and shore stations around the world. Between his job and his hobby, Kidder was undoubtedly one of the most skilled Morse code operators in the world. Other ham operators around the Pacific and across the United States were familiar with his call sign: PI 1HK.

“That’s forty-two states I’ve got now!” Kidder exclaimed. In his excitement, he’d forgotten the pickle he was in with the chief.

Chief Karcher took a deep breath and exhaled in Kidder’s face. It took all of Harry’s resolve not to react to the coffee and cigarette smell of the chief’s stale breath. “Kidder, you owe me thirty-five minutes extra duty,” he barked. “Relieve Johnson now, and see me after your watch is over.”

“Aye, aye, Chief,” Kidder responded immediately.

Extra duty was just another way of saying that Kidder would be swabbing the deck or shining the overhead for at least thirty-five minutes after his eight-hour shift ended. Karcher turned and walked off the watch floor. Immediately, the tension eased.

Kidder relieved Johnson and apologized in earnest this time. “I really am sorry, Jepp. I only got three hours of sleep.”

Everyone called Petty Officer Johnson by his nickname: Jepp. In the Philippines, the locals had a hard time pronouncing the f sound, and Phil had grown weary of the locals calling him “Pill.” He eventually began introducing himself to the Filipinos as Jeff, so from then on, his nickname became Jepp.

“It’s all right, Harry,” Jepp assured his buddy. “But you’re gonna have to show me that rig of yours someday.”

“You got it,” Harry answered.

Kidder put on the headphones and started his watch. His job was to monitor U.S. Navy transmissions on specific radio frequencies at certain times, otherwise known as “the sked.” The sked normally consisted of five to ten messages transmitted in Morse code from one naval station to another. At Camp Eldridge, most messages were destined for the headquarters of the Asiatic Fleet located in Cavite, about forty miles to the northwest. Other messages were to be retransmitted to U.S. Navy communications stations around the western Pacific Ocean.

To most Sailors, copying or sending Morse code messages was a difficult chore. To Harry, however, the dits and dahs were as clear as could be. While others struggled when the speed of the code reached twenty words per minute, Harry could easily copy thirty to forty words per minute. As he received messages addressed to ships and stations in the Philippines, he copied them and passed them to the on-duty yeoman. Other radio messages he relayed to other stations in the Asiatic Fleet before he passed them to the yeoman. On any given watch, a radioman at Camp Eldridge would likely talk to his counterparts at Pearl Harbor, Midway Island, Guam, Shanghai, and on board ships assigned to the Asiatic Fleet. For Kidder, his job was more like play than work, so his time on watch seemed to fly by.

Each shift, Kidder had seven regular frequencies to monitor—four in the high frequency (HF) band, two in the medium frequency (MF) band, and one in the low frequency (LF) band. This he did with the easy grace of a man who loves his work. In between skeds, Kidder would “spin and grin,” meaning that he would turn the dial to see what else he could hear. This was not part of his assigned duties, but his curiosity always got the best of him.

Other than being late, this shift was not unlike a thousand other watches Kidder had worked. He copied all the messages destined for his station and retransmitted everything he was supposed to. But on this particular day while spinning and grinning at the low end of the HF band, Harry came across a very loud signal in a military band and on a frequency that he wasn’t expecting. Knowing he’d have to leave it soon for his next sked, he jotted down the frequency—4255 kilocycles—and stuffed it in his pocket. He didn’t want the chief to know that he was listening to anything off-sked. He tried to copy the loud transmission, but something didn’t seem right. There seemed to be letters in the transmissions that he’d never heard before. He’d get a few letters, then miss a few. This frustrated Harry because he prided himself on a zero-mistake sked every time. This time, however, he was missing almost half the letters.

“What’s going on?” he muttered to himself. He shook his head as if there were wires crossed in his brain that needed uncrossing. He concentrated harder; it was still no good. The transmission was strong, the code crystal clear, but he was still missing letters in the message, and what he was able to catch made no sense. He kept at it for several minutes, trying his best to make some sense of it.

“The sked!” he scolded himself out loud for losing track of time and forgetting about his duties while trying to figure out the riddle of the unusual code he was hearing.

Kidder quickly tuned to the frequency of his next sked and got to it just after the call signs were sent. Thank God, he thought. The chief would have killed him if he missed his sked—especially after showing up to work late again. He could fill in the call signs on the copy sheet later before he gave it to the yeoman.

After completing his shift, Kidder made his way to the chief’s office, dreading the extra duty in store for him. He was still feeling annoyed about missing so many letters in that unusual transmission he’d heard; it just stuck in his craw.

As Kidder strode to the chief’s office, he knew he was in for some trouble. He only hoped Chief Karcher wouldn’t refer the issue to the commanding officer (CO). The last thing Kidder wanted was to face the old man at captain’s mast. The CO was notorious for taking a stripe from any Sailor brought before him for nonjudicial punishment, and Harry did not want to lose a stripe.

When he arrived at the chief’s office, he knocked loudly three times. “Petty Officer Kidder reporting as ordered, Chief,” he said steadily, trying to make a good impression.

“Come in,” ordered the chief.

Kidder entered the chief’s office and stood in front of his desk. The chief tapped his pencil on the steel desk at stared at Kidder. “Sit down, Kidder,” the chief snapped impatiently. Confused, Kidder did as he was told. Without taking his eyes off the Sailor, the chief put his pencil down, tapped a cigarette out of its cardboard box, lit it, and inhaled deeply.

On the desk, Kidder could see the chief’s coffee cup, half full of steaming black coffee. As if on cue, the chief took a sip. Inside the cup, Kidder saw the coffee stains that chief petty officers seemed to take pride in. “Don’t ever wash a chief’s coffee cup,” was well-known dogma within the U.S. Navy.

The prolonged silence was getting to Harry, so he finally blurted out, “I’m sorry, Chief. It won’t happen again.”

With his goal of getting Kidder to start the conversation achieved, Chief Karcher said, “Kidder, you know what happens if I’m late? Do you know what happens when a chief is late?”

“No, chief.”

“Well, first his Sailors begin to think they can come in late. And then the junior officers think they can come in late. Do you understand where I’m going with this, Kidder?”

Kidder had no idea, but he replied, “Yes, Chief.” He knew it was the only acceptable answer.

Chief Karcher exhaled loudly. He knew Petty Officer Kidder was the most talented communicator he had, but he didn’t like him. Kidder never went to the bars with his shipmates; he never even spent any time with the other Sailors. The only other navy man the chief ever saw Kidder talking to was a junior officer fresh out of the Naval Academy. They were both ham radio enthusiasts, and every time they spoke, it went over the chief’s head. To Karcher, Kidder was more than a little odd, and that irritated him.

“Kidder, what are you gonna do when you’re the chief? Are you gonna keep coming in late? Are you gonna set a bad example for your Sailors?” Karcher took another drag of his cigarette and tapped the ashes into the overflowing ashtray next to his coffee cup.

Harry had never given this any thought. Making chief was never a priority for him. And quite honestly, he didn’t think it was likely to happen, anyway.

“Well, no Chief, but I don’t see how that matters to—.”

Chief Karcher interrupted Kidder. “Don’t get smart with me, Kidder! It matters. Got it?” he barked.

Kidder was really lost now. “Yes, Chief.”

More silence followed as the chief took a drag of his cigarette and drank his coffee, never taking his eyes off Kidder. After what seemed like an eternity to Kidder, the chief took another deep breath, opened his desk drawer, and produced a single sheet of paper with letterhead from the Bureau of Naval Personnel (BUPERS). “The skipper received this letter from BUPERS today. It seems you’ve been selected for chief petty officer,” he said glumly.

“What?” Kidder said incredulously. “You’re joking.” Kidder knew that chief petty officers were the backbone of the Navy—senior enough to be wise, wise enough to know what’s important, and separate from the officer community so as to be able to call a spade a spade, when necessary. He just never thought of himself as worthy of selection to chief.

“I wish I was,” Karcher said flatly. “So, it’s going to go like this. After you pin on your anchors, you’re going to PCS in the fall. You’re headed to NAVCOMSTA Cheltenham, in Maryland. PCS is “permanent change of station” in navy parlance. In other words, Kidder was being transferred from his duties in the Philippines.

“That’s great, chief,” Harry said, half excited for his promotion and half sad to leave the Philippines.

“If you say so,” Karcher grumbled as he inhaled on his cigarette again. “You’ve got to make it through initiation, first, though.”

“Initiation, what’s that?” asked Kidder.

“You’ll find out, Kidder,” Karcher said. For the first time, Kidder detected the faintest of smiles on the chief’s face. “You’ll find out, all right.”

“Aye, chief.”

“Now, I want you to field day these spaces. Pick up every cigarette butt you find and empty every butt-can you see. I’m leaving for the day, Kidder. When I come in tomorrow, I don’t want to see a single cigarette butt anywhere in this building. I don’t care how long it takes you. Got it?”

“Aye, aye, Chief,” Kidder said dejectedly. He was hoping the news of him making chief would make Karcher forget about his extra duty.

“Start right here,” Karcher said as he dropped his cigarette on the floor and stamped it out slowly, all the while looking directly at Kidder. “Tomorrow, you and I are headed to Cavite to meet the other chief selectees.”

“But I’m off tomorrow, Chief.”

“You were off. You wanna be a chief, or not?”

“Yes, chief.”

“Then I’ll see you outside the front gate tomorrow morning at 0600 hours.”

“Aye, chief, 0600,” Kidder said as Chief Karcher got up. Kidder picked up a pair of work gloves and a garbage bag from the gear locker and began to pick up cigarette butts. Once he knew the chief was out of earshot, he mumbled to himself, “I’m never going to be an ass like Chief Karcher. I’m going to be a damn good chief!”

After about an hour, Kidder called it quits. He’d barely made a dent in clearing the room of cigarette butts, but he realized he was never going to pick them all up unless he worked overnight. His extra duty was only supposed to last thirty-five minutes, so he threw away the butts he’d picked up so far and left for the day.

As he walked home, Kidder was on top of the world. He was going to be a chief petty officer, something he never dreamed would happen. He whistled as he strolled through town, which was much livelier in the afternoon sun than it was earlier in the day. The afternoon heat was a joy to Kidder. The meat-on-a-stick vendors were back on the street, cooking on grills stoked by wood fires. Music emanated from every bar, as scantily dressed Filipina bar girls tried to coax him inside. It was early enough in the day that Sailors on liberty for the evening had not yet claimed them. As he walked through town toward his apartment, Harry was as happy as he could ever remember. Even so, something was bothering him—something underneath the happiness—like an itch he couldn’t reach.

Shaking the vague, uneasy feeling, he turned toward his apartment and saw several Filipino children playing in the street. When they saw him, they immediately ran over to him.

“Mr. Harry, Mr. Harry. Give me a penny. Give me a nickel,” they cried out. Harry chuckled to himself. Every day they asked him for change, and every day he told them no.

“Mr. Harry, we want bread,” they lied. He knew if he gave them money, they’d take it directly home, and bread was the last thing it would be used to buy. But this day was different. Harry had just found out he’d been selected for chief, so he was feeling generous. Without a word, he walked over to a fruit and vegetable stand on the street, the kids right on his heels. He reached down deep into his dungaree pocket for a quarter then picked out four apples. He gave one to each kid, who scampered off in all directions. He received his change from the shopkeeper and looked at it in his hand. Next to the fifteen cents was a crumpled piece of paper. What’s this, he thought, and then he remembered . . . the frequency!

Harry ran the rest of the way home. Stumbling toward the small desk in his bedroom, he turned on his ham rig. As the tubes began to warm up and glow, he leaned in close. He loved the faint odor of the capacitors heating up, the low glow of the vacuum tubes, the slight hum of the electronics at work—this was his bliss. When the familiar smell of capacitors and vacuum tubes began to fill the air, he knew the rig was ready.

He tuned to the frequency he’d written down earlier—4255 kilocycles—expecting the same loud unintelligible telegraphic code. Instead, he heard only static. Disappointed, he sat for a moment, wondering who the transmitter had been earlier in the day. It was a strong signal, so it must have been someone close by. But what were those strange characters? And why were they using a military band? They should have been on an amateur frequency band. He wished he had kept the copy from earlier. He listened to the static for twenty minutes but got nothing.

Harry was just about to give up and start tuning to an amateur band when he heard the telltale tuning of a continuous wave key.

..._ ..._ ..._


The signal sounded louder and stronger than before. The atmospherics must be good, Harry thought. Although he had a pair of headphones, he liked to copy using a speaker instead. He wore headphones all day at work, and the speaker allowed him to wander around his apartment while he listened. But not wanting to draw attention to himself through the open window in his bedroom, he turned down the speaker’s volume. Harry was determined to copy the code this time. Instinctively, he jotted down the time and frequency and began to copy. But it was no good. He couldn’t copy it. The telegraphic code proved to be just as indecipherable as before.

Who is this? He looked at his watch; it was ten minutes to six—ten minutes before the hour, just like it had been when he’d caught the transmission earlier in the day. They’re on a sked!

He was right. The transmissions continued throughout the night, beginning ten minutes before every hour and lasting between fifteen and twenty minutes. Each time the transmission came on the air, Harry copied all the letters he knew and recorded all the dit-dah combinations he didn’t. After each transmission, Harry scrutinized his copy—but he just couldn’t grasp what he was hearing.

“Dah dah dah dit dah,” Harry said aloud to himself. “What the hell is that?”

He copied sked after sked of jumbled code deep into the night, impatiently waiting between each one. Before the night was over, Harry Kidder realized he was copying some sort of telegraphic code with at least forty-eight characters in it. It had him completely stumped.

As the sun began to rise, Harry looked at the pile of papers on his desk: one recorded times and frequencies, the rest contained his copy. He could tell that there were call signs being used, and most of the transmissions seemed to be sent in groups of three characters. On a separate sheet of paper, Harry had written all the unknown dit-dah combinations he had heard throughout the night.

As the morning light crept in through his window, Harry realized he’d been up all night—again. At least it’s Sunday, so I don’t have to work today, and I can get some shut-eye, he thought. Sunday . . . Sunday? What’s different about this Sunday?

Harry looked at his clock, which read 07:21. He scratched his head as if to draw out the feeling he had that something was different about today . . . 

“Oh, no, I’m late. The chief!”

About the author

Matt Zullo is a retired US Navy Master Chief Petty Officer who has more than 35 years experience in Communications Intelligence. He holds a Master’s degree in Strategic Intelligence from the National Intelligence University, where he researched and wrote his master’s thesis on the On-the-Roof Gang. view profile

Published on August 10, 2020

100000 words

Worked with a Reedsy professional 🏆

Genre: Historical Fiction

Reviewed by