The Empire of Japan had a nuclear weapons program. Evidence was discovered after the war and may have been known to Allied intelligence during the war.
They cooperated in some technological matters with Nazi Germany as well; the bomb may have been one of them. They obtained several examples of tanks and aircraft and sent much needed material and supplies to Germany via submarine. It was at least a possibility that nuclear technology had been exported to the East to speed up the Japanese nuclear program, perhaps when the Germans knew they would lose the war. It was not known whether this was the case. The Germans came closer to making a bomb than the world was told in 1945 but the information was classified at the time.
Japan had several functioning submarines at the end of the war. Most importantly, they had developed and built examples of an aircraft carrying submarine which could launch and recover three bombers which could each carry an 1800 pound weapon. They built at least two examples of these subs as well as smaller aircraft carrying subs which could carry two of the bombers apiece. The I-400 and I-401's capabilities are well known because they both surrendered at the end of the war. Their airplanes had been launched into the sea or pushed overboard before the surrender, ostensibly because they were not marked according to the rules of war. They had ostensibly been sailing to attack the United States naval base at Ulithi.
Japan also had a biological weapons program in Manchuria, the infamous Unit 731.
The bioweapons could have been delivered by balloon, as crazy as it sounds. Japan had a program of stratosphere-riding fire balloons with which they tried to ignite North American forests. They did not succeed but several balloons reached the United States and one made it as far as Detroit. Some of their remaining conventional subs may also have been able to launch and recover small observation aircraft. One such submarine-borne aircraft actually tried bombing Oregon in 1942 but caused little damage as the plane was too small. Once again, we will never know for sure what the aircraft aboard the I-400 and I-401 were armed with because they were at sea at the time of Japan's surrender and their airplanes were launched into the sea or pushed overboard.
They cooperated in some technological matters with Nazi Germany as well; the bomb may have been one of them. They obtained several examples of tanks and aircraft and sent much needed material and supplies to Germany via submarine. It was at least a possibility that nuclear technology had been exported to the East to speed up the Japanese nuclear program, perhaps when the Germans knew they would lose the war. It was not known whether this was the case. The Germans came closer to making a bomb than the world was told in 1945 but the information was classified at the time.
Japan had several functioning submarines at the end of the war. Most importantly, they had developed and built examples of an aircraft carrying submarine which could launch and recover three bombers which could each carry an 1800 pound weapon. They built at least two examples of these subs as well as smaller aircraft carrying subs which could carry two of the bombers apiece. The I-400 and I-401's capabilities are well known because they both surrendered at the end of the war. Their airplanes had been launched into the sea or pushed overboard before the surrender, ostensibly because they were not marked according to the rules of war. They had ostensibly been sailing to attack the United States naval base at Ulithi.
Japan also had a biological weapons program in Manchuria, the infamous Unit 731.
The bioweapons could have been delivered by balloon, as crazy as it sounds. Japan had a program of stratosphere-riding fire balloons with which they tried to ignite North American forests. They did not succeed but several balloons reached the United States and one made it as far as Detroit. Some of their remaining conventional subs may also have been able to launch and recover small observation aircraft. One such submarine-borne aircraft actually tried bombing Oregon in 1942 but caused little damage as the plane was too small. Once again, we will never know for sure what the aircraft aboard the I-400 and I-401 were armed with because they were at sea at the time of Japan's surrender and their airplanes were launched into the sea or pushed overboard.