KOTA, Pakistan (Reuters) – Helicopter-borne Pakistani soldiers swooped into a Taliban stronghold in a remote corner of Swat on Tuesday, as the United Nations urged help for hundreds of thousands of people displaced by the fighting. The military's offensive in Swat, 130 km (80 miles) northwest of Islamabad, is seen as a test of the government's commitment to face up to a growing Taliban insurgency and comes after the United States accused it of "abdicating" to the militants. The fighting has caused a civilian exodus from the valley, once a tourist destination, raising fears of a humanitarian crisis. A senior...