Afghan war justification

WHY IS THE U.S. IN AFGHANISTAN?

The extremists in both Afghanistan and Pakistan include Al Qaeda, Lashkar-e-Taiba (now Jamaat ud-Dawa), the Taliban and several Mujahideen warlords, all of whom have 10s of thousands of supporters and are well armed and sophisticated.

The extremists are a great danger to nuclear armed Pakistan, whose government could easily be taken over by the above named groups.

Should that happen, nuclear armed India would be severely threatened by an extremist-controlled Pakistan. Fighting in Kashmir province would immediately intensify and we'd be looking at a huge conflagration in the area with nukes involved. The U.S. will not let that happen.
We are deploying U.S. troops to Afghanistan to be used as a buffer between several extremist groups in Afghanistan and the Pakistani government.

By later this year, the U.S. will have 70,000 troops in Afghanistan. There are already 71,000 private contractors and more being deployed. The UN-mandated International Security Assistance Force consists of 50,000 troops from 42 countries of which about 8300 are British troops.