Which event is characterized by Ambrose Burnside's futile frontal assault on entrenched Confederates?

The event characterized by Ambrose Burnside's futile frontal assault on entrenched Confederates is the Battle of Fredericksburg. This battle took place in December 1862 during the American Civil War and is infamous for the disastrous tactics employed by Union forces under Burnside. The Union army faced strong defensive positions held by Confederate troops led by General Robert E. Lee, who were well-positioned on high ground behind the town of Fredericksburg.

Burnside’s plan to attack the Confederates involved a series of ill-fated frontal assaults, where Union soldiers were charged directly at well-fortified positions. These assaults resulted in significant Union casualties without gaining meaningful ground. The heavy losses suffered by Burnside's troops underscored the perils of frontal assaults against entrenched positions, a lesson that would influence military strategy in subsequent battles.

In contrast, the other options—such as the Battle of New Orleans, which primarily involved naval forces and a very different context; the Battle of Borodino, which was fought during the Napoleonic Wars; and the Battle of the Plains of Abraham, a pivotal 18th-century engagement in the French and Indian War—do not relate to Burnside’s assaults or the tactical challenges of the Civil War.