The Syrian opposition took a big step forward this month by forming a broad political coalition that includes local activists who started the revolution. But the opposition’s military command is still a mess, and until it’s fixed, jihadist extremists will keep getting more powerful. As I wrote after my trip inside Syria in early October, a stronger command-and-control structure is crucial in creating an opposition force that can accomplish two essential tasks: defeating President Bashar al-Assad and maintaining order in Syria after he falls. The United States had encouraged the rebels to form provincial “military councils” to achieve better coordination. But the rebel forces have continued to splinter in recent weeks.