While ISIS’s videos of mass murder and murder-scene tweets once scared off its enemies, that approach is now having the opposite effect. Non-Sunni foes of ISIS, such as the Kurds in Kobani, believe they’ll be slaughtered even if they surrender—ISIS’s own publicity has convinced them of it—so they’re steeled for an all-or-nothing fight.

Before Kobani, the same logic had played out in other battles. The Shia town of Amerli managed to fend off ISIS attacks for months before American air power allowed the Iraqi army and Shia milita groups to break the siege.  

While Mosul showed what ISIS was capable of against a weakened enemy, the Kurdish town of Kobani is proving the limits of ISIS’s ability against a determined resistance.

Even before U.S. cargo planes dropped weapons and other critical supplies into Kobani on Sunday, the YPG, a Kurdish resistance group, had held off surrounding ISIS fighters for months. ISIS has penetrated into the city and launched attacks from three fronts but the Kurdish forces have so far held up their defense and kept Kobani from falling.