The attack yesterday saw 13 Americans killed when a suicide bomber struck an armored military bus in Kabul.
It was the single deadliest attack on U.S. citizens in the Afghan capital since the war began a decade ago.
It is the latest in a series of high profile actions by the Taliban who waged a prolonged gun-and-grenade battle aimed at the U.S. Embassy in Kabul and killed a key Afghan peace envoy and former president in a suicide bomb attack.
The drift in strategy says the report,is due to
the addition of 30,000 U.S. troops who have pushed insurgent fighters out of their rural havens in the south and made it harder for them to attack front-line U.S. combat forces.
Deadly attacks were relatively rare in Kabul but the new attacks underscore the resilience of the Taliban and difficulties NATO faces in keeping militants from attacking the heavily guarded capital.