The 10th Mountain Division was the first and only division of Mountaineers formed by the United States Army.
The 10th Mountain Division Light first unit, the 87th Regiment of Mountain Infantry, was activated on November 15, 1941. This was inspired by the Finnish Army's ski troops, who had caused significant problems for the Soviet Army during its invasion of Finland from late November 1939 to mid-March 1940. Following the Japanese attack on Pearl Harbor and America's entry into the war, training and completion of the 10th Mountain Division Light units accelerated sharply.
The 85th and 86th regiments were activated at the end of 1942.
Specific equipment and clothing suitable for mountain troops were studied and tested in the field in relation to the low temperatures in which they would be operating. Most of the men were experienced skiers or rock climbers, and their training took place in the high mountains surrounding Camp Hale, Colorado, which is over 2,000 meters above sea level and has cold, snowy conditions.
On November 6, 1944, shortly before leaving for the European front in Italy, the division was renamed the 10th Mountain Division.
The division consisted of three mountain infantry regiments (the 85th, 86th, and 87th), each of which was composed of three battalions. The battalions were composed of companies ranging from A to M.
In addition to the infantry, there were three battalions of light pack artillery (the 604th, 605th, and 616th battalions), as well as the 10th Mountain Anti-Tank Infantry Battalion, which consisted of the 727th Machine Gun Battalion and the 576th Anti-Tank Battery.
Combat forces were supported by a Medical Battalion with four medical companies and a veterinary company, a mounted reconnaissance group (10th Recon), the 110th Signal Company, and the 126th Mountain Engineer Battalion.

The following units were assigned to the Division in Italy for varying lengths of time: the 1125th Field Artillery Battalion, the 178th British Royal Field Artillery Regiment, the 701st Tank Destroyer Battalion, and the 751st Tank Battalion.
After nearly two years of training, the 86th Regiment embarked from Hampton Roads, Virginia, on December 11, 1944, bound for Naples on the ship USS Argentina, arriving on December 22.
Then, on January 4, 1945, the 85th and 87th regiments embarked from Hampton Roads on the USS West Point, bound for Naples. They arrived on January 13, 1945.
On January 6, the three artillery battalions boarded the USAT General Meigs, arriving in Naples on January 18, 1945.
The troops traveled in Italy by train from Naples to Livorno, then by military truck to staging areas near Pisa, to reach Italian territory at the foot of the Gothic Line.
From the waiting area in Quercianella, near Livorno, the 86th Regiment entered the front line north of Bagni di Lucca. Between January 8 and 9, 1945, they took over from Task Force 45 in the Monte Belvedere area. The 1st Brazilian Infantry Division, belonging to the Força Expedicionária Brasileira (F.E.B.), protected their right flank.
The 85th and 87th Regiments camped west of Pisa on January 15, 1945, and entered the front line on January 20 in the Monte Belvedere area.

From January 28 to 29, troops from the 85th and 87th regiments relieved the 86th regiment. The 86th regiment would later assault the German lines on the Riva Ridge (Pizzo di Campiano, Monte Cappel Buso, Monte Serrasiccia, Monte Mancinello, and Le Piagge) between February 18 and 19, 1945.
At 11 p.m. on February 19, 1945, General George P. Hays, commander of the 10th Mountain Division, ordered the three regiments to attack the Gothic Line. To accentuate the element of surprise, there was no preparatory artillery fire, as was customary.

The ground forces were supported by aerial reconnaissance led by "Rover Joe" and coordinated by the "Rover Pete" team on the ground.
The 87th Regiment's assault began near the village of Querciola and advanced towards Corona. The 2nd Battalion headed west toward the villages of Polla and Rocca Corneta. The 1st Battalion climbed the left ridge of Monte Belvedere at the same time as the 3rd Battalion of the 85th Regiment, immediately to their right.
Meanwhile, the 1st Battalion of the 85th Regiment stormed Monte Gorgolesco, and the 3rd Battalion of the 86th Regiment headed towards Mazzancana. The action continued toward Ronchidoso and Monte della Torraccia, finally conquered on February 24, 1945; Monte Terminale and Jola di Montese on March 3; Pietracolora on March 4; and Castel D'Aiano on March 5, 1945.
For the following four weeks, the three regiments of the 10th Mountain Division took up positions between Monte Castellaro, Monte Grande D'Aiano, Monte della Spe, Monte Sinistro, and Monte Castellana. During this time, the troops were sent in rotation to Prunetta and Campo Tizzoro, in the province of Pistoia and to Montecatini, for rest.
On April 14, 1945, the troops launched a final assault on the last remaining defenses of the Gothic Line, the final German stronghold before the Po Valley. The Spring Offensive led to the liberation of Rocca di Roffeno, Tolè, Monte Pastore, and Savigno on April 16.
The Via Emilia was crossed on April 20, near Ponte Samoggia, between Modena and Bologna, and the troops continued through the territories west of San Giovanni in Persiceto and Crevalcore towards Nonantola, Bomporto, and Bastiglia, which they reached on April 21. From April 23 to 24, the three regiments crossed the Po River near Governolo and occupied the Villafranca di Verona airport and Verona itself on April 25. On April 26, the troops reached the southern shore of Lake Garda and continued on to Torbole, entering it on April 30.
German troops in Italy surrendered on April 28, 1945, and laid down their arms on May 2.
On May 6, the 3rd Battalion, 86th Regiment met troops from the 44th Infantry Division of the U.S. Army, who were coming from Central Europe, near the Resia Pass in the Alps, between Italy and Austria.
On July 14, at dawn, the 10th Mountain Division, which had been stationed in Tarcento, near Udine, since May 20, together with British troops, was ordered to prevent any westward movement by Tito's partisan forces, who had occupied Trieste, Gorizia, and Klagenfurt.
During that time, the division received orders to return to the United States in preparation for the planned invasion of Kyushu, Japan, on November 2, 1945.
On August 6, 1945, the city of Hiroshima was destroyed by the first nuclear bomb in history. From July 26 to August 2, 1945, the three regiments of the 10th Mountain Division embarked for America from the ports of Livorno (86th Regiment) and Naples (85th and 87th Regiments). They arrived between August 7 and 11.
During the fighting in Italy, the 10th Mountain Division, consisting of 19,780 men, suffered 975 casualties and 3,871 wounded.
These were the highest losses suffered by an American division in Italy in relation to the time spent there.