He saved a lot more Japanese lives than he did American. Your million for the Americans sounds a little high. While estimates covered a wide range, the likely number would have been up to a million casualties on the allied side, with probably around 100,000 to 250,000 of those being deaths. Total war related military deaths to that point had been just over 400,000 for the Americans.
I think you’re right. 1 million casualties were predicted with 100 to 200 thousand deaths from the invasion.