U. S. leaders withdrew troops from Vietnam because

A. they believed the South Vietnamese could win it on their own.

B. the Viet Cong built supply trails in Cambodia.

C. the Soviet Union began bombing the south.

D. they realized that they could not win the war.

D. they realized that they cod not win the war.

. political or economical policy that isolates a country from participating in international relationships. it has been suggested that the united states participates in isolationism because of its lack of involvement in particular wars or alliances.