As a result of the atomic bombing or Hiroshima and Nagasaki, Japan surrendered without the need for an invasion of the home islands. So in spite of all the battles and struggles across the Pacific, the United States conducted no ground combat operations on the Japanese mainland.
The only American ground combat action on the Japanese home islands was conducted by the Navy, and it involved sailors from a U.S. submarine who destroyed a Japanese train.
The submarine USS Barb, commanded by Commander Eugene “Lucky” Fluckey already had a distinguished record of sinking Japanese shipping and warships when, on the night of July 23, 1945, in the bay off of Karafuto, Japan, eight men were put ashore in inflatable boats. Their mission was to set explosive charges to destroy a train on a Japanese rail line that ran along the coast. This was a very dangerous thing to do and there were plenty of ways for the mission to go wrong. The men got to the tracks and started to place the charge when a train came by in the other direction, causing the team to dive for cover.They places a pressure switch they had fabricated on board, so that the weight of the train on the track would set off the charge. The team headed back to the sub, but the next train appeared while they were still in the inflatable boat. The charge blew up the locomotive and caused the train to pile up behind it. The men reached the sub, that was waiting in dangerously shallow water to get as close to the shore as possible, and the USS Barb made its escape. The USS Barb had a number of other firsts, including being the first sub to deploy rockets in an attack, but nothing was quite like being the only submarine to destroy a train and the only American military unit involved in a ground combat operation in Japan in WWII.