From the Times:

ISLAMABAD, Pakistan — Pakistan moved large contingents of troops into the Taliban stronghold of South Waziristan on Saturday, beginning a long-anticipated ground offensive against Al Qaeda and Taliban militants in treacherous terrain that has overwhelmed the army in the past, the Pakistani Army said.
Military spokesman Maj. Gen. Athar Abbas said the attack was launched from three directions.
The operation is the most ambitious by the Pakistani Army against Taliban militants, who unleashed a torrent of attacks against top security installations in the past 10 days in anticipation of the assault. The militants’ targets included the army headquarters where planning for the new offensive has been under way for four months.
The United States has been pressing the Pakistani Army to move ahead with the campaign in South Waziristan, arguing that it was vital for Pakistan to show resolve against the Qaeda-fortified Pakistani Taliban, which now embraces a vast and dedicated network of militant groups arrayed against the state, including those nurtured by Pakistan to fight India.