Johnson stepped down in 1968 and did not seek re-election due to being discredited over Vietnam. Nixon implemented a Vietnamization policy from 1969-1973 to gradually replace American troops with South Vietnamese troops to allow the US to withdraw. However, the US struggled fighting guerilla forces, faced strong anti-war sentiment at home with many casualties and costs, and failed to win over the South Vietnamese people. Ultimately, the US lost in Vietnam as its military efforts were half-hearted and disillusioned, and the war fundamentally questioned America's beliefs about the president, military, and moral identity.