President Harry S. Truman led the effort to establish a single holiday for citizens to come together and thank our military members for their patriotic service in support of our country.
On August 31, 1949, Secretary of Defense Louis Johnson announced the creation of an Armed Forces Day to replace separate Army, Navy, Marine Corps and Air Force Days. (Defense.gov)
In the United States, Armed Forces Day is celebrated on the third Saturday in May. It falls near the end of Armed Forces Week, which begins on the second Saturday of May and ends on the third Sunday of May. (Wikipedia)