“Did the US demand Iranian Qassem Suliemani and his Kuds Force back off before helping the Iraqis in Tikrit?”
Apparently so. The US is reported to have insisted that operations be coordinated (i.e. commanded) out of the command center in Baghdad (rather than Suleimani’s hooch on Camp Speicher).
Ostensibly (and objectively) this is to minimize fratricide in the air operations. Effectively however, it means that the the Shia militias and Iranian special groups are shunted aside as failures.
The new plan is that they will sit across the river or outside of town, as the Iraqi Army walks over the rubble of the last ISIS strongholds and raises the flag in victory - provided of course that the Americans come across with enough air to wrap this up.
Or..
“Iraqi Shiite Muslim militias, angry that the government of Prime Minister Haider al-Abadi has asked for American help in ejecting Islamic State fighters from the central Iraqi city of Tikrit, began withdrawing their forces from the battle “
http://www.miamiherald.com/news/nation-world/world/article16416518.html
Probably the Iraqi army’s desire to go in as “the winners” is indeed the crux.