UNMANNED aircraft have begun targeting Taliban leader Baitullah Mehsud, a shift in strategy by the Obama administration that may reflect efforts to pre-empt a Taliban spring offensive against US forces in Afghanistan, the Washington Times reports. The US military avoided hitting Mehsud's forces in 2007 and 2008, during the Bush administration, when the Taliban leader waged a campaign of suicide bombings inside Pakistan. However, Mehsud formed an alliance last month with two other Taliban commanders in North and South Waziristan, a potentially significant development because territory controlled just by Mehsud does not touch the Afghan border. With the alliance, he now has an inlet to Afghanistan. Sarfaraz Khan, a professor at the University of Peshawar, traced the new US aggressiveness to the Taliban alliance. "In order to stop unifying Taliban groups from launching massive attacks against NATO and in particular newly arriving US troops in Afghanistan, such attacks have become indispensable on Americans' part," he said.