The area is thought to have been a key base for al-Qaida and Taliban fighters.
Four British companies, with about 120 troops each, left the Bagram Air Base north of Kabul for the area.
According to Pentagon officials, several hundred Afghan, Australian, British and American soldiers would participate in the operation.
Royal Marines Spokesman Lt. Col. Paul Harradine said U.S. troops and aircraft, including Apache attack helicopters and A-10 “Warthog” jets, are involved in the search mission, dubbed “Operation Snipe”.
With a total of 1,700 troops and support personnel, Operation Snipe is Britain’s largest combat deployment since the Gulf War.
Harradine said the sweep is taking place in territory that has not been searched before. He added that the first troops arrived in the region four days ago and have not yet encountered al-Qaida or Taliban fighters. He described the region as having “very rough terrain” with mountain peaks ranging from 8,000 to 13,000 feet.
Recent operations have focused on the towns of Khost and Gardez, as well as a region just across the Pakistan border. Allied troops have been searching area villages due to uncorroborated reports of top al-Qaida leaders in the area.
Once the British-led force secures the area to prevent al-Qaida and Taliban fighters an area to regroup, the troops will hand the area over to forces loyal to Hamid Karzai’s interim Afghan administration.
According to an Afghan Interior Ministry spokesman, hundreds of Karzai’s troops were also transferred to the region about 140 miles south of Kabul.
Since Operation Anaconda in early March, U.S.-led forces have continued to focus on eastern Afghanistan. Commanders have continued to send patrols through border regions to flush out al-Qaida and Taliban fighters, as well as weapons caches.