The American public largely ignored the war crimes trials in Tokyo and throughout Asia in 1946-1948. Unlike the charismatic Nazi leadership, who were infamous throughout Europe, the Japanese leadership was not well known. That was due in part to the Allied propaganda, which did not want to criminalize the Emperor. If the Allied public saw him as a criminal, they would demand his removal, which would have prolonged the war.
Hirohito's role in the conflict is not clear. He is generally seen as ineffectual, although there was some evidence offered in the 1990's that showed he was an active participant in the war planning. However, to maintain order in Japan, the Emperor was not indicted.
The Men put on trial in 1947 and 1948 were the first of 20,000 civilian and military former leaders who had either killed prisoners or had participated in the vague crime of instigating the war. While many would endure prison sentences of varying lengths, 900 were executed in trials around Asia.
Those executed included Hideki Tojo, General Masaharu Homma, Tomoyuki Yamashita, and five others who were blamed for atrocities during the war. The Japanese argued that they were subject to war crimes trials simply because of the heinous crimes of their German allies, essentially claiming the Allies were finding them guilty by association.