Bull Run, Battles of at English => English (The Britannica Concise) Of Explained:
Two engagements in the Amer. Civil War fought at a stream near Manassas, Va. The first battle (also called First Manassas) was fought on July 21, 1861, between 37,000 Union troops under Gen. Irvin McDowell (1818-1885) and 35,000 Confederate troops under P. G. T. Beauregard and J. Johnston. In this first major encounter of the war, the Union assault was beaten back and the army retreated to Washington, D.C. The second battle took place on August 29-30, 1862, between a Confederate force of over 56,000 under R. E. Lee and a Union army of over 70,000 under J. Pope. To prevent the Union force from being joined by the Army of the Potomac, Lee sent troops under S. Jackson to outflank the Union army. Lee's attack forced the Union troops to withdraw as far as Washington, D.C. Casualties numbered 15,000 for the North and 9,000 for the South. Both battles strengthened the South's resolve and caused the North to review its military leadership and strategy.