Ny Vietnam Battle; preferably The Hue City Battle

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The Battle of Hue City raises many questions because it seems that the outcome could have been markedly different had certain scenarios played out in the battle. Please reference these.
1. What was the impact of heavy gunfire support (in the form of artillery and naval gunfire support) on the Battle of Hue City? Many historians contend that many Allied losses could have been prevented had heavy gunfire support been approved earlier for the operations in Hue City (they had been prevented by South Vietnamese traditionalists wanting to preserve the sanctity of the city)
2) What would have happened if the North Vietnamese had been able to drop the main bridge across the Perfume River?