Union control of the Mississippi River began to tighten. On April 7, while the Confederates were retreating from Shiloh, Union Maj. Gen. John Pope defeated Beauregard's isolated force at Island Number 10, opening the river almost as far south as Memphis. On April 28, Admiral David Farragut captured New Orleans, the South's largest city and most significant seaport. Army Maj. Gen. Benjamin Butler occupied the city with a strong military government that caused considerable resentment among the civilian population.