How did the United States respond at the beginning of the war?

What are some incentives that parties have to carry out their campaign promises?

Which of these did the soviet union do in 1961? it built a wall through berlin to keep people from moving to the west. it used force to destroy a wall the united states had built in berlin. it convinced the british and french to merge their zones in berlin with the soviet zone. it threatened to bomb berlin if the united states did not leave within 30 days.

In general which explains why communist revolutions did not happen