In order to end the Vietnam War, American President Nixon finally made a secret commitment to North Vietnam via the “Soviet Union channel” after he took office: As long as Hanoi agreed to have “a decent interval” after signing the peace agreement, that is, Hanoi would not attack South Vietnam immediately after the U.S. forces withdrew, U.S. would allow it to unify Vietnam by war. Nixon’s secret commitment made North Vietnam eventually agree to sign the Paris Agreement.