On June 5, 1941, the U.S. Army drafted Roy Iwao Kawashiri, and in August Col. John Weckerling approached him for an interview. Weckerling tested his Japanese and then asked if he wanted to be a part of the Army language school, where he would receive a promotion to Sergeant upon graduation. Kawashiri, a San Francisco native, accepted the offer and in November 1941 started his training at the Military Intelligence Service Language School (MISLS).

Upon graduation and with a team of five other Nisei linguists, Kawashiri boarded a Liberty ship and left San Francisco for the Southwest Pacific in early May 1942. In the first few months of work, he helped translate two Japanese Naval codebooks that listed the names and codes of all the war and transport ships, and the Japanese Navy air force. Other members of his team interviewed the first captured POW, and although he volunteered for frontline service, Kawashiri watched as three others received orders to go to Guadalcanal to work closer to the frontlines.

Around December 1943, his Americal Division landed on Bougainville and secured the beachhead. All division headquarters personnel, including the language section, soon followed:

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Aside from our duties of translation and interrogation, we took turns listening in on the nightly Japanese radio broadcasts (Radio Tokyo)--translating the enemy's version of the war results and other news into English. [Autobiography]
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In addition, he wrote propaganda leaflets that Allied planes dropped over Japanese soldiers.

After the Bougainville campaign, the Americal Division landed on Leyte Island of the Philippines. Around that time, Kawashiri and six other Nisei linguists had accrued enough overseas duty to change their duties to stateside. The Army denied their request classifying them as "indispensable" and he continued his work on Los Negros Island, Philippines. 

On the island he worked with a Caucasian language officer, Lt. Hodgeson. One day at lunch, they went their separate ways, Hodgeson to the officer's tent and Kawashiri to the enlisted men's tent. As Kawashiri stood in line, everyone looked at him:

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Just as I was about to take my first mouthful, a Filipino soldier started yelling out loud, "An enemy soldier!" pointing his finger at me. Immediately, the mess sergeant and several men came dashing out of the tent and I was surrounded by them. The Filipino soldier took my food away. The sergeant approached me and just as he put his hand on my shoulder, I hurriedly told him that I was an interpreter here on temporary duty from division headquarters. Although I showed him my dog tags, he was still not convinced. Meanwhile, the Filipino scouts with their long machetes made me feel a bit nervous. I suppose they were in a state of bewilderment for none of the men said a word to me.
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Finally, Kawashiri remembered to call Lt. Hodgson who quickly explained the situation, but by that time Kawashiri had already felt the sergeant had been a little too rough. Later, when he learned that Japanese soldiers had actually infiltrated Allied chow lines by stealing Allied uniforms, he realized how difficult it was for the Caucasian soldiers to tell the difference between him and a Japanese soldier. As a result of that incident, Kawashiri received an escort for the rest of his stay on the island.

After finishing his duties on Los Negros Island, he received a 45 day Temporary Duty in the continental United States. The war ended and he requested a discharge. And on September 28, 1945, the Army officially discharged him of his duties.

