Here's one of the toasting pics you've seen:
WW2DB: [Photo] Chiang Kaishek and Mao Zedong celebrated the end of the Second Sino-Japanese War, Chongqing, China, Sep 1945
After the Xi'an Incident in Dec 1936, Chiang did get pressured to call for a ceasefire with the Communists in order to fight the Japanese together as one united China, but in actuality that never happened. Chiang struck at the Communists in small scales whenever he could get away with it, while the Communists made sure that most of the fighting against the Japanese were conducted with Nationalist troops while the Communist forces build up strength for the continuation of the Civil War that probably would, and did, take place almost immediately after the war against Japan would be won. The "friendship" between Chiang and Mao was artificial at best.
Here is a pic of Chiang and Stilwell together dated 1942, and then a big headshot of Chiang:
WW2DB: [Photo] Chiang Kaishek, General Joseph Stilwell, and Madame Chiang in Burma, 1942
WW2DB: Kaishek Chiang
Finally, a pic of Mao dated 1946:
Image:Mao1946.jpg - Wikipedia, the free encyclopedia
None of the folks in the Nanjing parade pic look like them, really.
Trust me, I wish it was such an easy identification! Hehe.