Thousands of U.S. Marines poured from helicopters and armored vehicles into Taliban-controlled villages in southern Afghanistan on Thursday in the first major operation under President Barack Obama's strategy to stabilize the country.

The offensive was launched shortly after 1 a.m. Thursday local time (4:30 p.m. EDT Wednesday, 2030 GMT Wednesday) in Helmand province, a Taliban stronghold and the world's largest opium poppy-producing area. The goal is to clear insurgents from the hotly contested region before the nation's Aug. 20 presidential election.