He deployed with the unit to North Africa in June 1943, participating in the amphibious assault on Sicily in July 1943, Salerno in September 1943, Southern France in August 1944 and also served in Alsace and Rhineland Campaigns.

[6] Treadwell was married to Maxine Johnson of Mooresville, Indiana, an Army nurse whom he met while he was recuperating in France from his most serious wound (a ricochet through his neck and chest).

Treadwell (then 1st Lt.), commanding officer of Company F, near Nieder-Wurzbach, Germany, in the Siegfried line, single-handedly captured 6 pillboxes and 18 prisoners.

Murderous enemy automatic and rifle fire with intermittent artillery bombardments had pinned down his company for hours at the base of a hill defended by concrete fortifications and interlocking trenches.

Over the terrain devoid of cover and swept by bullets, he fearlessly advanced, firing at the aperture of the nearest pillbox and, when within range, hurling grenades at it.

Never slackening his attack, he then ran across the crest of the hill to a third pillbox, traversing this distance in full view of hostile machine gunners and snipers.

The Germans quickly fell prey to his further rushes on 3 more pillboxes in the confusion and havoc caused by his whirlwind assaults and capture of their commander.

Inspired by the electrifying performance of their leader, the men of Company F stormed after him and overwhelmed resistance on the entire hill, driving a wedge into the Siegfried line and making it possible for their battalion to take its objective.

Treadwell reduced a heavily fortified, seemingly impregnable enemy sector.Treadwell's official Distinguished Service Cross citation reads:[7] The President of the United States of America, authorized by Act of Congress July 9, 1918, takes pleasure in presenting the Distinguished Service Cross to Second Lieutenant (Infantry) Jack LeMaster Treadwell, United States Army, for extraordinary heroism in connection with military operations against an armed enemy while serving with Company F, 180th Infantry Regiment, 45th Infantry Division, in action against enemy forces on 24 May 1944, near Carano, Italy.

Small groups of enemy under cover of artillery and mortar fire had advanced to within fifty yards of the company position and were beginning to infiltrate through the lines.

Closing with the enemy in fierce hand-to-hand combat, Lieutenant Treadwell inspired his men to a vicious and successful defense of their positions.