Importance of Mexican War

Led by General Winfield Scott, The U.S. Army invades Mexico in 1846-48, without explicit instructions from Congress about dealing with such crimes as murder, rape, assault, desecration, and theft committed by irregular troops. Scott responds by instituting martial law to maintain discipline and the honor of the U.S. Army, innovations not well received in Democrat-controlled Washington. It sets a precedent for using military commissions in the Civil War, their scope extended beyond the fighting troops to the civilian population suspected of disloyalty.