Experience proves that the man who obstructs a war in which his nation is engaged, no matter whether right or wrong, occupies no enviable place in life or history.
 Ulysses S. Grant, Personal Memoirs of Ulysses S. Grant (1885). copy citation

Context

“but if Mexico should attack our troops, the Executive could announce, "Whereas, war exists by the acts of, etc.," and prosecute the contest with vigor. Once initiated there were but few public men who would have the courage to oppose it. Experience proves that the man who obstructs a war in which his nation is engaged, no matter whether right or wrong, occupies no enviable place in life or history. Better for him, individually, to advocate "war, pestilence, and famine," than to act as obstructionist to a war already begun. The history of the defeated rebel will be honorable hereafter, compared with that of the Northern man who aided him by conspiring against his government while protected by it.” source