The Gatling gun is one of the best-known early rapid-fire spring loaded, hand cranked weapons and a forerunner of the modern machine gun. Invented by Richard Gatling, it is known for its use by the Union forces during the American Civil War in the 1860s, which was the first time it was employed in combat. Later, it was used again in numerous military conflicts, such as the Boshin War, the Anglo-Zulu War, and the assault on San Juan Hill during the Spanish–American War. It was also used by militias and the National Guard in episodes of the Great Railroad Strike of 1877, specifically in Pittsburgh, Pennsylvania.