The Last War (1961 film)

The Last War (世界大戦争 Sekai Daisensō, lit. "Great World War") is a 1961 Japanese film directed by Shūe Matsubayashi and distributed by Toho. The film follows a Japanese Merchantman's experiences before and during a Nuclear war.

Plot
Japanese merchantman Takano arrives back home with his crew after a long cruise and has a flashback to several months before, when he returned to Japan to propose to his girlfriend, Saeko Tamura, and ask for her father's blessing. Her own family continues to live life in relative peace and quiet. Despite reservations, the couple get married and spend one night in Yokohama before Takano ships out.

After Takano ships out tensions between the Federation and the Alliance (fictional stand-ins for the US and NATO against the USSR/Warsaw Pact, respectively) build up, especially after an intelligence-gathering vessel is captured. A new Korean War breaks out across the 38th parallel, but is quickly stopped. Although Japan calls on both sides to seek peace, government officials think that the country could be ripe for Alliance retaliation in light of its open support for the Federation. Dogfights between Federation and Alliance fighters over the Arctic (with both sides using nuclear-tipped air-to-air missiles) are just the beginning of a renewed conflict. The Alliance tips the scales by launching ICBMs on Japan and the West, with several cities totally destroyed. The Federation responds with their own nuclear strikes

It's revealed that Takano's ship has arrived to the remains of a decimated Tokyo as a children's song plays in the background.