Michael Hughes: There is little mystery over who is responsible for this week’s terrorist attack in Kabul, which Afghan intelligence officials have blamed on their Pakistani counterparts. The true dilemma lies in figuring out what is driving Pakistan’s calculus this time. The strategic depth doctrine is always at play which calls for “keeping the pot boiling” – as General Zia used to say – to prevent a stable, united, and independent Afghanistan from making decisions inimical to Pakistani interests, such as daring to align with India. But the timing, location, and profile of the attack suggest that it also might have been intended to send a message to the White House in a risky bid to test President Trump. Click here to read more.