What is the US Army motto?

The motto of the United States Army is "This We'll Defend." The origins of the phrase can be traced back to the setting up of the War Office of the Continental Congress in 1777 during the Revolutionary War.

The modern United States Army has its origins in the Continental Army, which was formed on June 14, 1775 to defend American liberty. On July 4, 1776, the United States became an independent nation, and the War Office was set up the subsequent year to be the intermediary of Congress between the Army and the states. The United States Army was officially started on June 3, 1784 by the Congress of the Confederation after the end of the Revolutionary War.