On March 10, 1864, President Abraham Lincoln signs a brief document officially promoting then-Major General Ulysses S. Grant to the rank of lieutenant general of the U.S. Army, tasking the future president with the job of leading all Union troops against the Confederate Army.

The rank of lieutenant general had not officially been used since 1798; at that time, President John Adams assigned the post to former President George Washington, in anticipation of a possible French invasion of the United States. One of Grant’s predecessors in the Civil War, Winfield Scott, had briefly earned the rank, but the appointment was only temporary—really, use of the rank had been suspended after George Washington’s death in 1799.

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In 1862, Lincoln asked Congress to revive the rank of lieutenant general in order to distinguish between the general in charge of all Union forces and other generals of equal rank who served under him in the field. Congress also wanted to reinstate the rank of lieutenant general, but only if Lincoln gave the rank to Grant. Lincoln had other ideas.

Lincoln preferred to promote then-Commanding General Henry Halleck to lead the Union Army, which had been plagued by a string of ineffective leaders and terrible losses in battle. He was reluctant to promote Grant and risk boosting the general’s popularity; at the time Washington was abuzz with rumors that many northern senators were considering nominating Grant instead of Lincoln at the 1864 Republican National Convention. After Grant publicly dismissed the idea of running for the presidency, Lincoln submitted to Congress’ choice and agreed to give Grant the revived rank. As lieutenant general of the U.S. Army, Grant was answerable only to Lincoln. Well-respected by troops and civilians, Grant earned Lincoln’s trust and went on to force the South’s surrender in 1865.

Although Grant enjoyed a distinguished career in the military, he later wrote that he never consciously chose the life of a soldier. As a student at West Point, he never expected to graduate, let alone lead the entire U.S. Army in a desperate but ultimately successful struggle to preserve the Union.

In 1869, Grant became the 18th president of the United States.