It had strangled the South. By blocking the southern coasts from the Carolinas to the Gulf of Mexico, and up and down the Mississippi, the Confederacy was locked in and out. It couldn't sell cotton and other staples to the outside world, and it couldn't import materials of war with the proceeds. All their own disciplined ferocity was now let loose. But the Civil War lives in American memory with undiminished intensity.
Every generation discovers it anew, especially in the South.
One cannot think of contemplate it without a pang of loss and sorrow. The last battle was Palmito Ranch. So, for a generation, the U.S. Navy and Army shrank to a tiny fraction of what they were in the War Between the States. Though Indian wars continued, and the Navy and Marines had some foreign adventures, essentially the country went back to the ways and business of peace. He was correct to a large degree, of course.