Palestinian President Mahmoud Abbas on Sunday named Gaza strongman Mohammed Dahlan as his national security adviser, presidential aides said. The appointment puts Dahlan, a top official in AbbasÂ’ Fatah party, in a sensitive position as Palestinian leaders try to reform their myriad and competing security services. As Gaza security chief in the 1990s, Dahlan led a crackdown on Hamas militants. The Islamic militant group, which is now in a unity government with Fatah, still has rocky relations with Dahlan.