What made Allied leaders worry about the cost of invading the Japanese mainland?

The Japanese put great emphasis on the Bushido code, which was a guideline of morals a samurai would follow, although samurai didn't exist anymore by WW2 the Japanese military still taught it's soldiers this code, which kept most Japanese soldiers from surrendering, the problem was is that the Japanese would keep fighting no matter what even if it meant getting themselves killed, the U.S. was already taking heavy casualties invading Japanese islands, if they invaded the mainland of Japan the casualties would be even worse for both sides, to prevent thousands of American soldiers from dying nuking Japan was the only solution seen by the Allied leaders.

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the committees of correspondence were the american colonies’ means for maintaining communication lines in the years before the revolutionary war. in 1764, boston formed the earliest committee of correspondence to encourage opposition to britain’s stiffening of customs enforcement and prohibition of american paper money. the following year, new york formed a similar committee to keep the other colonies notified of its actions in resisting the stamp act. in 1773, the virginia house of burgesses proposed that each colonial legislature appoint a committee for intercolonial correspondence. the exchanges that followed built solidarity during the turbulent times and bring about the formation of the first continental congress in 1774.