Why did the united states become involved in a war that was difficult for it to win

Assuming your question is in reference to the Vietnam War, the United States got involved because of

"Domino theory" was applied in justifying US involvement in the Vietnam War.  Domino theory said that the spread of communism in Vietnam would result in other countries in the region falling like dominoes to the influence of communism.  

Domino theory was a corollary to the overall policy of containment that developed as  the United States' policy regarding communism after the end of World War II.  George F. Kennan is known for recommending the policy of containment, which said that the best way to deal with the threat of communism was simply to try to keep it contained to the places where it already existed.  

the answer is b for brother

the dominoes began to fall. the surrender at appomattox took place a week later on april 9. while it was the most significant surrender to take place during the civil war, gen. robert e. lee, the confederacy's most respected commander, surrendered only his army of northern virginia to union gen. ulysses s. grant

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