A HIGH-PITCHED WHINING SOUND followed by a bang a few seconds later means a bullet is traveling in your general direction. In a firefight, due to the intensity and volume of bullets flying back and forth, these sounds become like white noise, swallowed by all the other sounds of battle. But a crack gets your attention—it means that a bullet just missed your head.

As they drew closer to the Iraqi Police station, the cracks increased in such frequency and volume that it sounded like popcorn popping. And Mac and his Marines knew that it was no longer a wild goose chase….