Pakistan, July 1 -- The message from the skies is becoming harder to ignore. On Tuesday, two rudimentary drones are said to have entered Pakistan's airspace from Afghanistan. They were shot down by the electronic warfare system. This has happened on the heels of a quadcopter killing a nine-year-old in Bajaur last week.

On the western front, the Afghan Taliban continue to deny that groups hostile to Pakistan enjoy space on their soil. Yet the attack pattern tells its own story. Drones are being used not only to attack but to probe, map, harass and test the country's defences. The frontier is no longer only a line crossed by armed men. Rather, it is becoming an air corridor for deniable violence.

The Afghan Taliban speak of dialogue, and ...