When did the United States join war?

World War I (1917-1918): The United States entered World War I on April 6, 1917, after Germany resumed unrestricted submarine warfare in the Atlantic Ocean, sinking several American merchant ships and causing the deaths of American citizens.

World War II (1941-1945): The United States formally entered World War II on December 8, 1941, the day after the Japanese attack on Pearl Harbor in Hawaii.

Korean War (1950-1953): The United States sent troops to South Korea under a United Nations mandate to repel the invasion by North Korea on June 25, 1950.

Vietnam War (1965-1973): The United States' official involvement in the Vietnam War began in 1965, when it committed ground combat troops to aid the South Vietnamese government against the communist forces supported by North Vietnam.

Gulf War (1990-1991): The United States joined a coalition of international forces to confront the invasion and annexation of Kuwait by Iraq on January 16, 1991.

War in Afghanistan (2001-2021): The United States launched the War in Afghanistan on October 7, 2001, in response to the terrorist attacks of September 11, 2001, which were orchestrated by al-Qaeda, a terrorist organization based in Afghanistan.

Iraq War (2003-2011): The United States invaded Iraq on March 20, 2003, citing the presence of weapons of mass destruction (WMDs) and Iraqi support for terrorism as the main reasons for the invasion.

These dates represent the formal entries or significant escalations of U.S. involvement in these wars.