This bears all the hallmarks of a Hezbollah type of operation.

They are set up along the line of task forces. ... They throw together whatever the elements they need to do the job at hand.

It would appear that it was a buried 50 kg (110 pound) device, and it may have been very simple. It was command (remotely) detonated at the front of the tank, blowing the engine clean out of the top of the tank and killing the driver instantly.

We suspect that the Taliban has a hundred useable tanks, which isn't that many. On the books they probably have 600, but most of those are inoperative.