During the Second World War, Ueda was an anti-aircraft gunner assigned to several merchant ships. He served on about 28 merchant ships, and 6 of those were attacked and destroyed while he was aboard. During his spare time, he would draw ships. On 13 November 1944, while assigned to Kinka Maru, he was severely injured during a U.S. air raid on Manila Bay. He lost the use of his right hand, but subsequently was able to draw and paint with his left hand.