From the very beginning. IJN subs were prowling the US west coast and launched submarine airplanes which bombed Oregon, and fired shells from their deck guns into Santa Barbara California.
There were five midget Japanese submarines : I-16, I-18, I-20, I-22, and I-24 .
During World War 2, it is reported that over 2,000 variants of Japanese Submarines were used during World War 2. Out of this, it is estimated that 10,000s were likely to be used during WW2.
The Imperial Japanese Navy started World War II with one of the largest submarine forces in the world. Despite the sinking during the war of several major U.S. warships by Japanese submarines, the Japanese were never able to effectively employ their submarines to any great extent. Japanese submarines tended to operate alone and were directed toward tactical gains. The United States, in contrast, employed wolf packs, embraced new technology, and engaged in a campaign of strategic submarine warfare. On Dec. 7, 1941, during the attack on Pearl Harbor, there where 3 Japanese submarines stationed in a picket line 100 miles forward of the carriers. They were the I-23, I-21, and I-19. There are even rumors of Japanese subs patrolling the East Coast during the war.
The U.S. had 111 submarines in commission at the start of World War II and commissioned 203 more before the war ended.
In World War 2
Some Japanese submarines were used in the Indian ocean, but none had enough range to reach Europe.
Why don't you just Google "World War 1 Submarines?"
World War I submarines were primarily used to locate and attack surface cargo and warships.
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this is where they got help
Submarines changed war. They played a big part of World War I and II.
At the time of the attack on Pearl Harbor, the U.S. Navy had 111 submarines in commission. It commissioned 203 more during the course of the war.