The Harraz and the Harrazhariya

The only stretch of land that could allow them to enter medina 10,000 strong so their numbers prove to be a negative against them had they been 10 you cannot stop 10 people from coming. The rest of medina that was in the direction of the army attacking were plantations date palms and when you have dense date palms you cannot have 10,000 men marching through it. This is the only logical response and frankly it's the most obvious one.