The Marshall Plan let the US give billions of dollars to European countries to rebuild after World War 2. Economically, it helped Europe to regroup and make them more stable. Around this time, the US was getting worried about Communism spreading through the European countries, named the Domino Effect, because if one country fell to Communism, they all would. So if the US could make the countries of Europe economically stable, then they would be less likely to let a Communist leader take over.