British troops in Helmand say they rarely get a clear shot at Taliban attackers, who ambush them with improvised explosive devices, rocket-propelled grenades and assault rifles. The explosive devices  some made with fertilizer distributed to Afghan farmers in an effort to wean them from opium production  are the most feared weapon. The Taliban favor ambushes in the morning and evening and do not often strike during the blazing afternoon heat.

In recent weeks some British troops have been setting up what are known as “blocking positions” on bridges over irrigation canals and at other locations, apparently to help stop the flow of insurgents during the main military operation and to establish greater security before the presidential election scheduled for August. The British forces, whose main base in Helmand is adjacent to the main Marine base, will continue to support the new operation.

Image U.S. Marines walking toward a helicopter transport at Camp Dwyer. Credit... Manpreet Romana/Agence France-Presse — Getty Images

The British have had too few troops to conduct full-scale counterinsurgency operations and have often relied on heavy aerial weapons, including bombs and helicopter gunships, to attack suspected fighters and their hideouts. The strategy has alienated much of the population because of the potential for civilian deaths.

Now, the Marines say their new mission, called Operation Khanjar, will include more troops and resources than ever before, as well as a commitment by the troops to live and patrol near population centers to ensure that residents are protected. More than 600 Afghan soldiers and police officers are also involved.