"That guard is made up of fighters loyal to Mahmoud Abbas, the Palestinian president and Fatah leader, and his recently chosen national security adviser, Muhammad Dahlan. It seemed no accident on Tuesday that Hamas chose to attack the training base of the Presidential Guard, near the Karni crossing, which the Fatah men are supposed to protect under Washington’s latest security plan for Gaza. The attack seemed aimed as much at the United States for siding with Fatah as at the guardsmen themselves, who did not fight very well, witnesses said. Mr. Dahlan, though abroad, ordered a brigade undergoing training in Egypt to return to Gaza, another measure of the stakes for Fatah there, where there are no Israeli troops to keep Hamas underground."