U.S. forces have now surpassed 2,800 strikes against targets in Iraq andSyria under President Obama’s war against the Islamic State, all as part of a conflict Congress has yet to specifically authorize — and amid worries lawmakers won’t ever act.

Under intense pressure from Capitol Hill, Mr. Obama finally submitted a draft authorization for the use of military force against the Islamic State in February, but it’s since languished, caught in the stalemate between those who want tighter restrictions and those who want the president to have as free a hand as possible.