Marines Drive Into Afghan Stronghold

After days of anticipation, the Marines of the 3rd Battalion rolled out in the early hours of Saturday morning and headed for Marjah.

Updated at 7:46 p.m. ET

After days of anticipation, the Marines of the 3rd Battalion rolled out from this outpost in the early hours of Saturday morning and headed for Marjah. At dawn, a drone flying overhead spotted an improvised bomb that was laid in their path. The drone fired a hellfire missile, and the Marines moved forward, reports CBS News Correspondent Mandy Clark.

The biggest coalition offensive in more than eight years was underway Saturday night in Afghanistan, centered on the Taliban stronghold of Helmand province in the south. Special Report: Afghanistan

The Taliban has put up a fight in several places around the city of Marjah and the Marines were taking no risks. The owner of a sprawling compound was ordered out by the Taliban so the Marines conducted a search, ever mindful of the dangers of the booby traps that have become the Taliban's weapon of choice. The compound was abandoned and the Marines moved on.

Approaching Marjah from the north, the troops had to get over the irrigation canals that surround the city. India Company was busy building a footbridge when it came under intense fire. The Marines and their Afghan partners returned fire, but the Taliban had been preparing for this assault and were determined to keep the bridge from being built.

Meanwhile, further east, Lima Company was more successful. The Marines quickly built a footbridge and marched finally into the besieged city.

All around Marjah Saturday, coalition forces have been flooding in. Helicopters landed some forces right at the heart of the city, while British, American and Afghan troops have been erecting bridges, clearing mines and exchanging fire with the enemy. So far, one Marine and one British soldier have been killed and several coalition soldiers have been injured.

Three other Americans were reported dead Saturday in an unrelated action.

In Washington, President Obama received multiple updates through the White House Situation Room on the operation in Marjah, a White House spokesman told CBS News Correspondent Mark Knoller. The president planned to speak to Gen. Jim Jones, Mr. Obama's national security adviser, about the operation Saturday evening.

On Sunday morning, Gen. Stanley McChrystal, the top U.S. military commander in Afghanistan, is expected to brief Mr. Obama, the spokesman said.

The Taliban are certainly not giving up on this town without a fight. They have had weeks to plant explosives and fortify their positions. The Marines are moving with what they call tactical patience, clearing their path as they go, but they say they won't stop until they've taken the entire city.