"What made Hue a bloody house to house slugfest, was the Prohibition on Artillery and CAS. So the Marines resorted to using Recoiless Rifles and then mortars."
The Vietnamese government at first wouldn't allow use of artillery, heavy armor, or CAS in Hue, hoping to preserve its important buildings. It was also the middle of the monsoon season, meaning that CAS was pretty much out of the picture no matter what the policy.
But, that ban was lifted part way through the battle. That still meant, however, that heavy armor couldn't maneuver well in Hue's streets, and it was still monsoon season, and artillery is not a sure thing against the kind of buildings that were to be found in Hue, a combination of very durable masonry and, in the outskirts, concrete.
Recoilless rifles, on the other hand, could be used almost surgically to much greater effect.
By the time Marines began to assault the citadel, the monsoon season had lifted and it was routinely bombed and napalmed by US aircraft.
