What was the main purpose of submarine warfare in World War II?

The main purpose of submarine warfare in World War II was to disrupt the enemy's supply lines and to damage their naval capabilities without direct surface combat. Submarines were effective in this role due to their ability to approach undetected beneath the surface of the water and launch surprise attacks against merchant and military ships.

During World War II, the navies of several nations, including Germany, Britain, the United States, and Japan, utilized submarines to great effect. The German U-boats, in particular, targeted the shipping lanes across the Atlantic in an effort to cut off Britain from vital supplies, a campaign known as the Battle of the Atlantic. Similarly, the United States used submarines in the Pacific Theatre to attack Japanese supply lines and reduce Japan's ability to sustain its forces across various islands.

Submarine warfare was also a means to reduce the naval strength of the opposition by sinking warships and aiming at the tonnage of merchant shipping, thus impairing the enemy's logistics and economy.

Submarine warfare is a facet of naval strategy that uses the stealth and undersea mobility of submarines to gain a tactical advantage. During World War II, the development and use of submarines revolutionized naval combat. Submarines operated primarily as lone wolves, often staying submerged during the day to avoid detection and surfacing at night to attack or recharge batteries and replenish air.

The element of surprise that submarines afforded made them formidable weapons against both merchant shipping and warships. They could lay several types of mines as well as use torpedoes to sink ships. Moreover, their ability to operate unnoticed allowed them to conduct reconnaissance missions and support special operations.

The warfare conducted by submarines also had a psychological impact, creating a constant threat to surface ships. As a countermeasure, various antisubmarine warfare (ASW) techniques and technologies were developed, such as depth charges, improved sonar, and convoy systems where merchant ships traveled in groups protected by warships.

The strategic impact of submarine warfare was significant. It could tie up a disproportionate number of enemy ships in ASW roles, meaning that for every submarine at sea, an enemy might need to deploy dozens of ships for protection, thus affecting their operational capability elsewhere. Submarine warfare, therefore, proved to be both a direct threat to maritime logistics and a strategic diversion of enemy resources during World War II.