After a year, he briefly visited his home in Bryant and then returned to Texas, this time working as a waiter in Colorado City.

He returned to the U.S. and served out the rest of his enlistment with the 28th Infantry's Company G.[2] After leaving the Army, he worked briefly in Berkeley, California, before acquiring a job as a railway mail clerk with the U.S.

In this capacity, Miller apprehended illegal immigrants, assembled cases against smugglers, and patrolled land and water routes across the U.S.–Mexico border and along the California coastline.

[4] Resigning from his job with the immigration service, Miller re-enlisted in the U.S. Army on May 16, 1917, shortly after the United States' official entry into World War I.

He attended a reserve officer training camp in Presidio, California, and performed well enough to be one of two people promoted to major upon graduation.

After 2 days of intense physical and mental strain, during which Maj. Miller had led his battalion in the front line of the advance through the forest of Argonne, the enemy was met in a prepared position south of Gesnes.

Just before the objective was reached he received a wound in the abdomen, which forced him to the ground, but he continued to urge his men on, telling them to push on to the next ridge and leave him where he lay.