Urban combat is terrifying. In an open field a tank is pretty hard to counter since they can see further and shoot better than a person. It's very hard to hide, especially from IR.
In a city there is almost an uncountable number of places for someone to hide and launch an ambush. They can get extremely close to a target without being detected, which opens up a lot of options for anti-tank warfare. They can also block paths extremely easily (with say a dried up cement truck) and neutralize combat vehicles. They also have a good idea of where you will be when planting IEDs, unlike in a wide open field.
In a city there is almost an uncountable number of places for someone to hide and launch an ambush. They can get extremely close to a target without being detected, which opens up a lot of options for anti-tank warfare. They can also block paths extremely easily (with say a dried up cement truck) and neutralize combat vehicles. They also have a good idea of where you will be when planting IEDs, unlike in a wide open field.