What was the role of the 39th infantry regiment in the invasion of north Africa?

The 39th Infantry Regiment was part of the 9th Infantry Division and was formed into the 39th Regimental Combat Teamfor the invasion.

Quoting from Center for Military History website:

http://www.history.army.mil/brochures/Algeria/Algeria.htm

Map:

http://www.history.army.mil/brochuresalgeriap24(map).jpg

Of the three TORCH task forces, Eastern Task Forceincluded the largest British proportion. Not only were naval and air support British; so were 23,000 of the total 33,000 troops. The 10,000 U.S. Army troops landing at Algiers would consist of Col. Benjamin F. Caffey, Jr.'s 39th Regimental Combat Teamfrom the 9th Infantry Division; and Col. John W. O'Daniel's 168th Regimental Combat Team and Lt. Col. Edwin T. Swenson's 3d Battalion, 135th Infantry, both from the 34th Infantry Division. These American units and all British Army units in the initial landing were under command of U.S. Maj. Gen. Charles W. Ryder. Naval support included a Royal Navy flotilla of 3 aircraft carriers, 4 cruisers, I antiaircraft vessel, 7 destroyers, and 15 transports. Enemy strength was estimated at 15,000 troops with only obsolete tanks, 91 fighters and bombers at two airfields, 12 coastal batteries, and a few destroyers in the harbor.

At Beach CHARLIE, however, coastal batteries fired on transports as the landing craft neared shore. Naval gunfire responded, but then high surf scattered 39th Regimental Combat Team boats, smashing some against coastal rocks. Leaving the boats, most troops found, instead of gradually rising ground, a vertical bluff with stairs cut for sightseers. Overcoming all these difficulties, the troops of the 39th Team moved eight miles inland and took the airfield at Maison Blanche by 0830. But for the rest of the day a fierce battle raged with a French marine artillery battery. Royal Navy surface and air units eventually prevailed, though Axis bombers managed to damage a transport and destroyer.

AnswerDuring the famous Battle of Kasserine Pass, the Americans had to pull together as many replacements to fill in the line. On Friday(19 Feb), the reinforcements included the regimental band, a tank platoon, and three companies of the 39th Infantry Regiment.

Most of the time, the 39th Regiment spent time in Algeria doing guard duty. However, in March, the 9th Division was sent into the front lines and suffered 1,812 casualties (~10%) in one week.

Reference: "An Army at Dawn" by Bill Atkinson