London - The Margalla Hills offer breathtaking vistas of Pakistan's federal capital, Islamabad. On a clear day, picnic-goers can see from historic Faisal Mosque to Rawalpindi, home of Pakistan's military nerve center. One day soon, however, this national park's densely forested hills could also provide perfect cover for Taliban fighters to rain down rocket-propelled grenades and shoulder-fired surface-to-air missiles on Islamabad itself.

The Taliban's bid to seize control of Pakistan is now clearly mapped out after its forces this week overtook Buner district, home to about a million Pakistanis just 70 miles from the capital. Top US military official Mike Mullen is in Islamabad for emergency meetings, and Pakistan has sent in...