Call Of Duty 4: Never Ending Battle?

I was playing the level War Pig on COD 4 and i just pretty much ran through the whole level but when i got to the end where the enemy tank was there was just a never ending wave of arabs. The Abrams tank would move up to destroy the enemy tank. So i sat there for 2 hours killing the soldiers and they still kept coming! Idk if it was a glitch or what cause this never happened before. I just finally had to quite when i ran out of amo. Whats the deal?