These photos should help answer your question when it is a conventional war
These photos are of the highway between Kuwait city and Basra in 1991 they were called the highway of death. The Iraqi army started pulling out of Kuwait in a massive convoy.
The US military bombed them. first Navy A-6 intruders hit the lead vehicles with cluster bombs
Then for 10 hours US aircraft bombed and strafed the column. This was done because the military operates under the assumption that a retreating enemy is simply running to fight someplace else.
In a counter-insurgency, it gets a little dicier since part of their goal is to pacify a population and that requires winning the hearts and minds