The second annual Kumagai Cup tournament took place on Sunday, February 2, 1941. "Guess who won it," recalled Hank Ogawa many years later. "Matsuo Sakagami. I wasn't there to defend it. I was in Los Angeles, and I had to send the trophy back to Seattle."

The third (and final) Kumagai Cup competition took place on Sunday, November 16, 1941. Seattle Dojo's Dick Yamasaki won the cup, while his teammate Yozo Sato took second. Seattle Dojo also took first in the team competition and the junior competition.

The Seattle Dojo closed following the Japanese attack on Pearl Harbor in December 1941. During the spring of 1942 the US Army moved Japanese Americans living in exclusion zones throughout the western United States into concentration camps known as relocation centers. So from 1942-1946 the Seattle Dojo building was used to store personal property that its members couldn't take with them.

After the war most relocated Japanese Americans returned to Seattle. Some reestablished their stores, shops, and hotels. Others went to college on the GI Bill. And some just got drunk and stayed that way. The city had changed, the people had changed, and nobody was quite sure if the change was good or not. After getting off the bus at Second and Main in 1946, wrote John Okada in The No-No Boy:

he walked toward the railroad depot where the tower with the clocks on four sides was. It was dirty looking tower of ancient brick. It was dirty city. Dirtier, certainly, than it had a right to be after only four years... [Jackson Street, with its familiar storefronts and taverns] had about it the air of a carnival without quite succeeding as one. A shooting gallery stood where once had been a clothing store; fish and chips had replaced a jewelry shop; and a bunch of Negroes were horsing around raucously in front of a pool parlor. Everything looked older and dirtier and shabbier.

Of course it took most people several years to adjust, and to decide with a character in Okada's novel that:

One must live in the real world. One must live naturally, not so? It is not always a happy life, but sad or happy, it can be a good life. It is like the seasons. It cannot always be the fall. I like the fall.

At first the new dojo didn't have many students. As a result in March 1947 the local businessman Henry Okuda gave some prewar judo uniforms still in their bags to Masato Tamura in Chicago. But the Seattle instructors persevered, and with the help of the Seattle Buddhist Temple and the Nisei Veterans Committee, the club survived.

By 1949 the Seattle Dojo had enough students to justify being open two nights a week. Training took place Mondays and Thursdays from 7:00 to 10:00 p.m. As classes were geared mostly toward juniors aged eight to fourteen, senior members often got copies of the key so that they could train other days.

In November 1950 the Seattle Yudanshakai supported a plan to turn judo into a national sport recognized by the Amateur Athletic Union (AAU). "We wanted a national judo shorn of factional localism," recalled Robert W. Smith, who was then active in the movement for the national judo organization. "With great effort we got it. Then we got two national organizations. I don't know how many now and today (July 1997) we have jacketed wrestling sans ethos. We were demi-Frankensteins and we had a baby!"

In November 1951 the Seattle Dojo supported the reopening of the judo club in Vancouver, British Columbia, by providing forty tatami. Due to problems importing rice straw into Canada, this seemingly simple transaction required six months of negotiations.

During the Korean War relations between the United States and Japan improved. Indicative of the improving relations was a Seattle trade show in July 1952 that showed Japanese-made judo uniforms. (For the past decade most US judo uniforms had been locally hand-sewn.) Interest in judo grew, and in August 1952 a Puget Sound Yudanshakai was created.

The rejuvenated Seattle Dojo was mentioned in an article appearing in the Seattle Post-Intelligencer on January 15, 1953. The club also gave a televised demonstration two weeks later during the half-time festivities at a basketball game between Seattle University and Loyola. The organizer and commentator of the latter event was a Seattle University student named George Wilson and the demonstrators included Sam Furuta and Ted Shinoda.