The more than 100 U.S. Navy intelligence code-breakers who played a key role in the World War II victory against Japan were honored in ceremonies at Pearl Harbor on Monday, the 74th anniversary of the Battle of Midway.

Sworn to secrecy, most of the code-breakers never received public recognition during their lifetime.

“That honor was being denied them while they were doing their work here,” said Capt. Dale C. Rielage, director of intelligence and information at the Pacific Fleet.

A commemoration was held before news cameras at Building 1, also known as Station HYPO, where the intelligence unit worked in secret in the basement, intercepting and interpreting Japanese communications during the war. The basement is now used mainly as a storage area.

The Battle of Midway, June 4-6, 1942, is viewed by many historians as the key turning point in the war against Japan because the United States was able to cripple Japan’s carrier fleet and halt its expansion in the Pacific.

The battle resulted in the destruction of four Japanese carriers and 256 aircraft and the deaths of more than 2,204 Japanese sailors and aviators. The U.S., by comparison, lost one carrier, 150 aircraft and 307 men, according to the Navy.

“That broke the back of Japanese naval aviation,” said Brad Sekigawa, historian at the Naval Air Museum at Barbers Point. After the battle, he said, the Japanese lacked a sufficient number of experienced personnel to develop its naval fleet.

Burl Burlingame, historian at the Pacific Aviation Museum, said the Battle of Midway showed that, contrary to some who felt naval destroyers were the primary weapons in battle in WWII, carriers and aircraft could also play a pivotal role.

He said in the battle, U.S. dive bombers were able to penetrate the Japanese defenses.

Before the battle got underway, the Pearl Harbor- based intelligence unit, led by Cmdr. Joseph J. Rochefort, knew Japan was mounting naval forces at a place called “AF” and suspected that AF was Midway but needed to confirm the location, Rielage said.

Rochefort’s combat intelligence unit had the naval station at Midway send an unencrypted message noting that Midway’s desalinization unit wasn’t working.

Days later the combat intelligence unit intercepted a Japanese message that mentioned the desalinization unit wasn’t working at AF, confirming that Japanese forces were mounting an attack at Midway.

Rielage said through the 1940s and the early 1950s, not even the official naval historian was aware of the code-breakers’ role in the Battle of Midway.

The Navy declassified some information about the code-breakers at Pearl Harbor in the 1970s as a film about the Battle of Midway was being produced, and declassified all the information in the 1980s.

Rochefort, who died in 1976, was posthumously awarded a Distinguished Service Medal in 1985 and awarded the Presidential Medal of Freedom in 1986.