How did modern technology help decide the outcome of the First Battle of Bull Run?

Answer 1

While the railways were not a new technology, what was new was the use of railways in battles and in wars. The rail link to where Confederate Johnston's forces were located, and Bull Run, where the armies of Union General McDowell and Confederate General Beauregard were to square off, helped unite the Southern armies and become the deciding factor in the Southern victory at the First Battle of Bull Run.But the railways were a tool to improve upon a military tactic that dated back to the Napoleonic Era. It was known as " interior lines". There were no Union troops standing between those of McDowell and Beauregard. The two Southern armies were thus linked by lines that were interior from the battle front.

Any lines of reinforcement to McDowell were not linked. There were "exterior" to the site of the battle action.

Both Union General Henry Wager Halleck and Southern General PT Beauregard had read about these tactics long ago. They would be a vital consideration throughout the Civil War.