Coalition forces in Afghanistan are spreading out across the south of the country. Commanders say it’s their biggest offensive against rebels since the fall of the Taliban regime five years ago. Eleven thousand troops are taking part in the offensive, named Mountain Thrust, in four southern provinces.Forces include soldiers from the US, Britain, Canada as well as Afghan units. Details were kept secret until a few hours ago. The operation started last month. It is aimed against suspected Taliban bases in the mountainous zone on the Pakistan border. There has been an increase in clashes with Taliban fighters in recent weeks in the region. One American soldier and a serviceman of unknown nationality were killed in the latest operations, according to coalition headquarters.