The night of December 7, 1941 was a panicked one in Hawaii. In the wake of Japan’s surprise attack on Pearl Harbor, Hawaiian civilians struggled to understand what had just happened—and to make sense of the announcement that their island was now under martial law.

As military and FBI agents rounded up suspected spies and “suspicious persons,” the army imposed a strict curfew. Habeas corpus was suspended, the military took control of labor, and trial by jury was temporarily abolished. More than 2,000 people were arrested in the first 48 hours alone. Hawaii would remain under military rule for almost three years.

“The Army's readiness to take over every detail of government in Hawaii only hours after the Pearl Harbor attack was in startling contrast to its lack of military preparedness to deal with the onslaught by Japan's air fleet,” writes legal historians Harry N. Scheiber and Jane L. Scheiber.

Military rule meant big changes for Hawaiians. Every person on the island, with the exception of children, was fingerprinted and issued identification papers they had to produce on demand. Civilians were banned from photographing any coastal location. Hawaii’s Japanese Americans, who had long been under surveillance by federal and military intelligence agencies that feared they would side with Japan during wartime, were treated particularly harshly.

At the time, Hawaii was a territory, not a state. The law that established a territorial government in 1900 covered Hawaiians with the protections of the United States’ constitution. Thirty-seven percent of residents were of Japanese descent, including 37,000 Issei (Japanese-born people who were not eligible for citizenship) and 121,000 Japanese American citizens.

Hawaii’s proximity to Japan made it of prime strategic importance, and put the islands at unique risk. But military officials doubted the loyalties of the island’s many Japanese Americans. As the United States sent people of Japanese descent to internment camps on the mainland, it vacillated as to how to deal with Japanese Americans in Hawaii itself.

The federal government couldn’t afford to intern one-third of the population of Hawaii: The war effort needed labor and feared such a move might stoke pro-Japanese sentiment. Besides, the logistics of imprisoning nearly 160,000 people in a territory that was small to begin with seemed insurmountable. And so, they turned the Hawaiian Islands into its own type of internment facility instead.

“I wasn’t supposed to speak Japanese anymore,” said Jane Kurahara, who was a young girl in Honolulu during the Pearl Harbor attack, in an oral history. “It was almost like a sin.”

“The community was fearful of...being taken away,” recalled Tomoko Hisamoto in an oral history interview. She was 17 when Pearl Harbor was bombed. Her father, a Buddhist priest and Japanese language school teacher, was swept up in an FBI raid soon after the attacks. Though she had enjoyed a thriving Japanese community in the years before the war, under martial law she was shunned by her former friends. “We were totally isolated.”

Many of the period’s rules focused specifically on non-citizens who had been born in Japan. Japanese-born people couldn’t own shortwave radios, gather in groups of more than ten people, or move without requesting official permission. They were labeled “enemy aliens.”

Other facets of military rule applied to all Hawaiian civilians. “Everybody was under martial law and treated equally unfairly because the military couldn’t target just the Japanese, who were so important to the economy,” historian DeSoto Brown told the Huffington Post.

During martial law, the media was censored, and press outlets were only allowed to use English. So were people placing long-distance calls. The Japanese language ban affected schools, which were forced to close. Hawaii’s Japanese population had long been subjected to English-only campaigns, but they had never been successful. Now, pressure to speak only English came from both the military and Japanese groups desperate to prove their loyalty to the United States. “Speak American,” encouraged one campaign.

Though it was not military policy to intern people of Japanese descent in Hawaii, dual citizens, community leaders and suspected spies were rounded up and detained. They underwent military hearings during which they were not told of the nature of their accusations. About 10,000 people were arrested and 2,000 incarcerated, one-third of them American citizens. Others who wished to be repatriated to Japan were held in internment camps in the mainland United States.

“Our daily life in the camp was monotonous and empty; eat and sleep, eat and sleep,” recalled Jack Tasaka, who was interned at Honouliuli. Though many in the camp relished their occasional supervised family visits, he recalled, others hoped their families and friends would not come. “They were afraid visitors might be arrested one after another upon their visits,” he wrote.

People could be arrested and interrogated at random, and hasty, biased hearings were common. According to Scheiber and Scheiber, this policy of “selective detention” had a chilling effect on Hawaiian civilians, who restricted their movements and lived in fear of arrest and harassment.

"My father lived in constant fear of being sent to a concentration camp, as my Uncle Toru Nishikawa had been. Uncle Toru, born in Hawai‘i, was deemed a threat to national security because he was a reporter for a Japanese language newspaper in Honolulu," wrote Jean Ariyoshi, the former first lady of Hawaii, in Washington Place: A First Lady’s Story. "He was locked up on Sand Island and later moved to Honouliuli Internment Camp on O’ahu. His bank account was frozen and his wife’s sewing school forced to close."

Despite being subjected to such harsh restrictions, it turned out that people of Japanese descent did not betray the United States as feared. “With the exception of Otto Kuehn, a German immigrant who was convicted of espionage, not a single one of the internees or detainees was found guilty of overt acts against U.S. laws, no one was investigated for sabotage, and only a few were suspected of espionage,” they write.

The policy had roots in the history of Hawaii as a territory. World War II wasn’t the first time the territory was threatened with martial law, or racked with discrimination and suspicion based on race. In the 1930s, for example, white civilians and military officials had called for martial law after a group of Japanese men were falsely accused of the rape and murder of Thalia Massie, a white Navy wife.

In the 1920s, the U.S. Army developed a joint defense plan along with the U.S. Navy that would impose martial law in Hawaii if the U.S. and Japan ever went to war. Then in the 1930s, the U.S. Army presented the federal War Plans Division with a report that painted “an apocalyptic picture of Japanese-American disloyalty and danger,” according to historian Greg Robinson. Steeped in racist language, the report laid the foundation for the martial law that would be imposed a few years later.

In October 1941, territorial officials in Hawaii enacted the Hawaii Defense Act, a law that gave the civilian governor broad powers but that ensured due process. But the bombing of Pearl Harbor in December 1941 swept those plans under the rug. The Pearl Harbor naval base was attacked at 7:48 a.m. By 3:30 p.m., President Roosevelt had approved the territorial governor’s plan to declare martial law.

Hawaii's governor, Joseph Poindexter, later claimed he had been convinced of its necessity by U.S. military commander Walter C. Short and believed it would only last 30 days. Martial law stripped Poindexter of his authority over the territory and handed it over to military control instead.

As time dragged on, so did martial law. Even after the Battle of Midway in June 1942, which was widely thought to have ended the possibility of a Japanese invasion, military control continued. in early 1943, Hawaii’s new civilian governor and a group of influential civilians petitioned the Roosevelt Administration for an end to military rule. The military strenuously objected, and only agreed to turn over some control if it was allowed to continue its regulation and control of labor.

Hawaii finally got some of its civilian government back in March 1943. But only in October 1944 did martial law end. Even then, though, full control of Hawaii was not returned to civilians. Those designated “enemy aliens” were still ruled by the same restrictions, and the U.S. Army still controlled Hawaiian labor.

Martial law was finally over, but it left a bitter taste in the mouths of many Hawaiian civilians. In 1946, that discontent made its way to the United States Supreme Court. In Duncan v. Kahanamoku, a Hawaiian civilian protested his arrest and prosecution by the military commission for a minor offense during martial law. He won: In the majority opinion, Justice Hugo Black wrote that, “Our system of government clearly is the antithesis of total military rule ...This supremacy of the civil over the military is one of our great heritages.”

Though the case is little remembered today, it was a reminder that Hawaiian civilians had sacrificed their freedoms during the war—demonstrating a loyalty that would become a critical argument for statehood 13 years later, when Hawaii was admitted into the union as the 50th state.

READ MORE: How Measles Helped Destroy the Hawaiian Monarchy