Major General Waheed Arshad said the troops are to perform a large-scale operation against several thousand militants led by Maulana Fazlullah, the leader of Tehrik Nifaz-e-Sharia Mohammed, a pro-Taliban militant group.
Swat valley lies in Pakistan's North-West Frontier Province and was, until recently, popular with tourists for its Buddhist sites and moderate climate.
However, Swat saw an increase in militant activity after Fazlullah, speaking on an illegal FM radio station in July, announced a jihad, or 'holy struggle,' against Pakistani authorities. Other unidentified extremists have also burnt TV sets, computers and video equipment, local media reported.
There are also reports that Islamists have partially destroyed a seventh-century statue of Buddha in Swat valley.
In the past few years, Pakistani tribal areas have seen an influx of al-Qaeda and Taliban militants from neighboring Afghanistan.