The US and allies have killed hundreds, but enemy ranks have been renewed.
SHAHI KOT, AFGHANISTAN
This is how the battle is playing out: Al Qaeda fighters, usually in pairs, jump out from cave entrances in the snow-covered mountain peaks and fire rocket-propelled grenades and antiaircraft missiles at US positions in the valley below.
B-52s - 10 to 15 minutes later - pummel the cave dwellers, while a US special forces team heads higher into the mountains. Their faces camouflaged, and flanked by 50 Afghan soldiers, the US troops advance in three jeeps and two all-terrain motorbikes.
As the seventh day of the largest offensive in the Afghan war began, the US significantly beefed up its presence with both US special forces troops and their Afghan allies. But at the same time, Al Qaeda and Taliban fighters strengthened their positions.
It's become clear that Operation Anaconda, which was expected to last only 72 hours, is a much tougher battle than the US expected. Both sides have suffered painful loses. Although the US has placed more than 1,000 troops on the ground to supplement their Afghan allies, they haven't been able to completely block the Al Qaeda fighters' routes in and out. The Al Qaeda and Taliban fighters - using Stinger missiles left over from the US operation here in the 1980s and led by Mullah Mohammed Omar's military commander - are hunkering down for a do-or-die showdown.
Local residents in the village of Shahi Kot say there are some 800 to 1,500 hard-line Taliban and Al Qaeda fighters - mainly Chechens - holed up here. They apparently regrouped in these fortified mountain complexes after they fled from Tora Bora, Kandahar, and Kabul earlier in the war.
Gen. Tommy Franks, commander of US forces in Afghanistan, said the number of Americans in the operation has grown by 200 to 300 over the past two days, and now totals roughly 1,100. They joined about 1,000 US-backed Afghan fighters and a small number of elite, special operations troops from six nations.
"I think the days ahead are going to continue to be dangerous days for our forces," General Franks said in Washington on Wednesday. He also raised the possibility of sending in even more firepower, including additional transport aircraft, infantry, and special operations troops. He described the situation on the ground as "very messy."