Operation Moshtarak, meaning "together" in the Dari language, is the biggest coalition attack since the Taliban fell in 2001.
Troops taking part in the offensive have been having to deal with large numbers of improvised bombs. American forces have found a so-called "daisy chain" - a long bomb rigged up from mortar bombs, rocket-propelled grenades and a motorbike, our correspondent says. And British engineers have deployed a device called a "python" - a length of explosives designed to set off mines and clear a safe path through them, he says. Meanwhile, to the north, British forces have discovered an insurgent cache of stolen Afghan army and police uniforms. The find suggests the Taliban could have been planning attacks disguised as Afghan security personnel, our correspondent says. BBC, 26 02 2010