So starts the seige of Baghdad—next they will turn off the elecricity and water-—watch for bombs to go off and aircraft shot down at the airport—the next big battlefield.
Most infrastructure outside of the Kurdish areas travel along the banks of the Tigris and Euphrates - roads, power, comms, etc. Something like 90% of the Arab population lives within a few miles of the rivers (walking distance)
If they take both banks of the river South of Baghdad they can cut some significant supply and services.
They will also be crazy close to the Holy city of Karbala, which should be the Shia’s biggest red line.