After Japan's defeat he was imprisoned for a time, accused of war crimes, and then found financial success in various business ventures, including motorboat-racing gambling events (Kyōtei) and ship building.

In the 1930s, during the Sino-Japanese War, Sasakawa rose to prominence by using wealth gained in rice speculation[2] to build a voluntary flying squad within Japan for the purpose of providing trained pilots in case of a national emergency.

[3] In 1939, Sasakawa flew his air squadron to Rome to meet his personal hero Benito Mussolini, whom he admired as "the perfect fascist and dictator".

Once Japan began to coordinate its air power in 1941, Sasakawa dissolved his voluntary flying group and gave all of its facilities and aircraft to the nation.

[18] However, his efforts in this vein were largely unsuccessful, and he spent much of the war outside of the Diet, touring Manchuria and China, visiting prisons around the country, and cheering those on the home front.

Along with his friends Syngman Rhee, the first President of Korea, and Chiang Kai-shek, the Chinese nationalist leader, he founded the World Anti-Communist League.

[30][31][32] From 1968 to 1972, Sasakawa was the honorary president and patron of the Japanese branch of International Federation for Victory over Communism (Kokusai Shokyo Rengo), which would forge intimate ties with Japan's conservative politicians.

[33][34] Allen Tate Wood, a former top American political leader of the Unification Church of the United States, recalled his surprise upon hearing Sasakawa telling an audience, referring to himself, "I am Mr. Moon’s dog".

Sasakawa later publicized photos of what appeared to be a valuable cargo of gold bullion, platinum ingots, and British sovereigns, as well as crates of precious jewels.

Sasakawa claimed that the treasure was worth over $36 billion in modern currency, but offered to turn it over to the Soviet Union, in return for the Kuril Islands to Japan.

Sasakawa's credibility was completely ruined when it turned out that the metal shards he allegedly recovered from aboard the Admiral Nakhimov had the density of lead, but not platinum.

Under this law, motorboat races are held at 24 locations around the nation for the purpose of both bolstering the local economies and providing the revenue needed to support 1) the reconstruction of Japan's maritime industry, and 2) welfare projects around the country.

The system of farming out former government employees to businesses and foundations has long been a common, legal practice in Japan, though one that Sasakawa himself viewed with suspicion.