GARMSIR, Afghanistan, July 19 – Marines pushing deep into a Taliban stronghold in Afghanistan’s southern Helmand province battled insurgents in a day of firefights around a key bazaar Sunday, as an operation designed as a US show of force confronted resistance from Taliban fighters as well as constraints on supplies and manpower.

Insurgents at times showed unexpected boldness as they used machine guns, mortars and rocket-propelled grenades to fight the advancing Marine forces. Although the Marines overpowered the Taliban with more sophisticated weapons, including attack helicopters, the clashes also indicated that the drive by about 4500 Marines to dislodge the Taliban from its heartland in Helmand is running up against logistical hurdles.