I will buy that al-Qaeda members are communicating more frequently between the three countries, but couldn't this also be just a result of AQAP growing stronger?
Certainly, Nasir al-Wahayshi has built a durable and flexible infrastructure in the country that could absorb a number of new fighters, I've been arguing this for quite a while, but I don't think there is any evidence that foreign fighters have made their way to Yemen. AQAP is certainly getting stronger and growing in terms of men, I think that is clear, but what is not clear is whether these men are all from Saudi and Yemen or whether they are from other countries. I'm skeptical on the latter.
It seems as though intelligence agencies are seeing some of the people they watch move out of a particular area of Pakistan, and then guessing that they must be going to either Yemen or Somalia because A.) the groups are now communicating and B.) because this would be a logical place for them to go - The US is worried about Yemen and Somalia becoming terrorist havens, ergo any terrorists that start traveling must be going there. I'm not sure it is this simple.
Also the second clause of this line is demonstrably untrue: "It could also swell the ranks of a growing menace in Yemen, where militants now control large areas of the country outside the capital."
AQAP does not control large areas of the country, and to say it does gives a mistaken impression of Yemen. It is a cheap and misleading line, hopefully dropped in by editors who have never been to the country looking to add some color and not written by a journalist who has actually visited Yemen.
Finally, it appears some were not impressed with the Kilcullen/Exum op-ed on drones in Pakistan:
"Some aides to President Obama attribute the moves to pressure from intensified drone attacks against Qaeda operatives in Pakistan, after years of unsuccessful American efforts to dislodge the terrorist group from their haven there."If the unnamed officials in the piece are correct that these fighters are moving to Yemen and if they believe they forced them out of Pakistan with drone attacks, I would caution them against applying the same tactic to Yemen, where the US would quickly find itself on the wrong end of a number of tribal conflicts.