Yamamoto was a son of a Samurai, and opposed the war. He insisted that the US will never stop fighting and the war will continue for several years, and Japan should not start the war with little chance of success. In fact, he said to take every effort to avoid war with America. But he was overruled and ordered to go ahead.
He knew that Japan could sustain a war fand win for six months, but beyond that over years they are going to be losers.
Much later on when Japan was on the losing stint, when they lost Solomon Islands, Yamamoto & his chief of staff boarded an aircraft to getaway. They both took off in two separate Mitsibishi bombers.
Sadly they didn't know that their secret communications has been broken by the US by this time. The US knew about this and ordered these to be shot down. There were no survivors. Several days later a search party found the bodies, then cremated, and the ashes returned to Japan.
There was a recent book "
Dead Reckoning" by Dick Lehr, (Award winning author & a Professor of Journalism) which describes the "Operation Vengeance" - the targeted killing of Admiral Yamamoto. Read it if you can. It shows the human side of Yamamoto and his honour. He insisted that US be notified that there's a "state of war" existed between the two countries before the attacks took place.