Philip St. George Cooke

Philip St. George Cooke (June 13, 1809 – March 20, 1895) was a career United States Army cavalry officer who served as a Union General in the American Civil War. He is noted for his authorship of an Army cavalry manual, and is sometimes called the "Father of the U.S. Cavalry." His service in the Civil War was significant, but was eclipsed in prominence by the contributions made by his famous son in law, J.E.B. Stuart, to the Confederate States Army.
At the start of the American Civil War, the U.S. Army had five mounted regiments. Cooke commanded the 2nd Dragoons, which was redesignated the 2nd U.S. Cavalry. As they prepared to ride into their first battles, they had the potential opportunity to learn from the two-volume manual on cavalry tactics written by Cooke in 1858, but not published until 1862. It was a controversial work at the time and the War Department chose not to make it the basis for official doctrine.
The issue of secession deeply divided Cooke's family. Cooke himself remained loyal to the Union, but his son, John Rogers Cooke, became an infantry brigade commander in the Army of Northern Virginia. J.E.B. Stuart, the famous Confederate cavalry commander, was Cooke's son-in-law. Cooke and Stuart never spoke again, Stuart saying, "He will regret it only once, and that will be continually."
After the Peninsula, Cooke left active field service. One proximate reason was the embarrassment he suffered when his son-in-law, J.E.B. Stuart, humiliated the Union cavalry by completely encircling the Army of the Potomac in his celebrated raid.
https://en.wikipedia.org/wiki/Philip_St._George_Cooke