WASHINGTON (AP) — Thousands of U.S. Marines and hundreds of Afghan troops moved into Taliban-infested villages with armor and helicopters Wednesday evening in the first major operation under President Barack Obama’s revamped strategy to stabilize Afghanistan. The offensive was launched shortly after 1 a.m. Thursday local time in Helmand province, a Taliban stronghold in the southern part of the country. The goal is to clear insurgents from the hotly contested Helmand River Valley before the nation’s Aug. 20 presidential election. Dubbed Operation Khanjar, or “Strike of the Sword,” the military push was described by officials as the largest and fastest-moving of the war’s new phase. British forces last week led similar missions to fight and clear out insurgents in Helmand and neighboring Kandahar provinces. The Pentagon is deploying 21,000 additional troops to Afghanistan in time for the elections and expects the total number of U.S. forces there to reach 68,000 by year’s end.