Operation Sword was focusing on communities along the Euphrates River between the towns of Hit and Haditha in the volatile Anbar province (search), said Marine Capt. Jeffrey Pool, a spokesman.
The region, about 125 miles northwest of Baghdad (search), is a hotbed of terrorist activity.
The U.S. troops include Marines, soldiers and sailors from Regimental Combat Team 2, comprised of the 2nd Marine Regiment and 2nd Brigade Combat Team of the 2nd Marine Division, Pool said.
Operation Sword, or Saif in Arabic, comes on the heels of two other offensives — dubbed Operations Spear and Dagger.
Operation Spear was aimed at stemming the flow of foreign fighters over the porous Syrian border in Karabilah, which is near the Iraqi frontier town of Qaim. The U.S. military said nearly 50 insurgents were killed during the five-day operation.
A senior Al Qaeda leader who was wanted in Saudi Arabia was killed during the offensive, said Al Qaeda in Iraq's leader Abu Musab al-Zarqawi in an Internet posting.
Operation Dagger took place north of Baghdad, and was charged with uprooting foreign-fighter networks.