The 2003 war lasted 1 month, 1 week and 4 days (Wikipedia) The invasion tactic was shock and awe. They didn't plan to occupy, they thought it would be easier

The 2003 war lasted 1 month, 1 week and 4 days (Wikipedia) The invasion tactic was shock and awe. They didn't plan to occupy, they thought it would be easier to setup a puppet government than it was. They couldn't leave until Iraq was in a state to balance Iran's regional influence. USA wanted to use Iraq for a oil/gas pipeline to Europe from Saudi/Qatar. They realised that was not possible due to the USA lack of state building abilities. So they turned their attention on Syria for the pipeline. Jordan agreed but Syria was a under the Russian sphere of influence, so they needed to topple this government for the pipeline. The pipeline would have challenged Russian oil/gas monopoly in Europe.