Why are US, allies telling Taliban about coming offensive?

Thousands of U.S., British and Afghan troops are poised to launch the biggest offensive of the war in Afghanistan in a test of the Obama administration's new counterinsurgency strategy. Military operations usually are intended to catch the enemy off guard, but for weeks U.S. and allied officials have been telling reporters about their forthcoming assault on Marjah, a Taliban-held town of 80,000 and drug-trafficking hub in southern poppy-growing Helmand province. Senior NATO commanders and top Afghan officials have openly discussed the approximate time of Operation Moshtarak–the Dari language word for "together"–the size of the force and their objectives in news conferences, interviews and press releases that have been disseminated around the world and posted on government Web sites. Leaflets have been airdropped on the town.