By renaming the Defense Department the Department of War, President Trump will restore the name that had been used until shortly after World War II.

The executive order on the name change, which the White House said Mr. Trump would sign on Friday, will also make good on a pledge he had made for months. Mr. Trump has argued that “defense” was too politically correct a term, and that War Department “just sounded better.”

Here’s what to know about the name.

What’s the history of the name?

George Washington established the Department of War in August 1789, months after the Constitution was ratified and he became the first president. The department oversaw the new nation’s military forces. Its first secretary was Henry Knox, who had served as a commander during the Revolutionary War and had, since 1785, been the war secretary under the Articles of Confederation, an early agreement among the colonial states.

The name was retained for more than 150 years, during which time the United States fought wars against Britain, Spain, Mexico and the Philippines, as well as the Civil War. It also fought wars against Native Americans.

The United States entered World War I in 1917 and, after the attack on the U.S. base at Pearl Harbor in 1941, joined World War II on the side of the Allied powers. When Mr. Trump floated the idea of the name change in August, he said it would be a reminder of U.S. military victories under the old name, citing World War I and II.

Why was the name changed to the Defense Department?

According to the Truman Library Institute, President Harry S. Truman changed the name as part of the National Security Act he signed in 1947, a time when the United States was the world’s only nuclear power and the Cold War was just starting.