Redesignated ARNORTH in 2004, it was first activated in early January 1943 as the United States Fifth Army, under the command of Lieutenant General Mark W. Clark.

The first iteration of the Fifth Army was authorized by the National Defense Act of 1920, and was originally to be composed of Organized Reserve units primarily from the Fourth, Fifth, and Sixth Corps Areas.

[7] The United States Fifth Army was initially commanded by Lieutenant General Mark Clark, who would lead the Fifth Army for nearly two years,[8] and was to experience some of the toughest fighting of World War II, where it was engaged on the Italian Front, which was, in many ways, often more reminiscent of the trench warfare of the Western Front in World War I.

Writing to Lieutenant General Jacob L. Devers (American deputy to Field Marshal Sir Henry Maitland Wilson, Mediterranean Theater commander)[9] in late March 1944, Clark explained the difficulties of the fighting in Italy so far, which could be said of the whole campaign.

They were, he claimed, "Terrain, weather, carefully prepared defensive positions in the mountains, determined and well-trained enemy troops, grossly inadequate means at our disposal while on the offensive, with approximately equal forces to the defender.

[15] With the failure of the first operations to capture Monte Cassino, an attempt was made to exploit the Allied preponderance in seapower before the coming invasion of Normandy robbed the Mediterranean of the naval forces necessary for an amphibious assault to seize Rome.

VI Corps landed at Anzio, unopposed,[17] on 22 January 1944 in Operation Shingle, and suffered many of the same problems as had been seen at Salerno.

A perceived lack of initiative on the part of the commander, Major General Lucas, combined with worries about the Germans catching VI Corps off balance if it advanced too far inland resulted in the beachhead being bottled up.

However, the dividing line was shifted westwards, to allow the concentration of both armies on the western side of Italy for maximum firepower to break through to Rome.

[21] However, in contravention of orders, Clark diverted units of VI Corps towards Rome, leaving a small blocking force to attempt to stop the Germans.

Clark claimed that there were significant German threats which necessitated the diversion, but many believe that he was primarily glory-seeking by being the first to liberate Rome.

The Allied forces spent another winter, after fierce fighting in the summer and autumn in front of the Gothic Line, frustrated at their lack of ability to break through.

This time Fifth Army, with British XIII Corps under command, led by Lieutenant-General Sidney Kirkman (whose relationship with Clark was apparently very stormy) was straddling the Apennines, with many of its units occupying high, exposed positions which were miserable to garrison.

The German units, in the main, were pinned against the Po River and destroyed, or at the very least deprived of their transport and heavy weapons, which effectively made many of them useless.

IV Corps pushed due north through Verona, Vicenza and as far as Bolzano and to the Brenner Pass, where they linked up with elements of the U.S.

[27] In the informal athletic competitions held between units of the European and North African theaters, the Fifth Army was among the most successful, winning titles in baseball, boxing, swimming and football during the 1944 season.

[28] (Part of 15th Army Group) The Army's next role was considerably less violent, and it was reactivated on 11 June 1946 at Chicago under the command of Major General John P. Lucas, who had commanded U.S. VI Corps in the early stages of the Battle of Anzio (Operation Shingle) during World War II before being relieved.

Joint Task Force-Civil Support, a subordinate command, is designated as the Department of Defense (DoD) command element for Department of Defense assistance to the overall federal response to a state governments request for assistance in the event of a catastrophic chemical, biological, nuclear or high yield explosive CBRNE emergency.