The greatest length of active service as a general in the U.S. Army was Winfield Scott who held the rank from 1814 to 1861, when he resigned seven months after the start of the Civil War because President Lincoln stopped listening to him. General Grant arguably did, however, a few years later. Grant’s victorious strategy was quite similar to the “Anaconda Plan” of strangling the South initially promoted by Scott.
Winfield Scott William Lawrence Sr Omnibit 4-11-19
