The Mutual Defense Assistance Act commonly known as the Battle Act was a 1949 law passed by the United States.

The act was part of the American Cold War strategy of containment. The act had a number of sections. Most importantly it promised assistance to any ally that might be attacked by the Soviet Union, or one of its allies.

It also cut off all aid and economic assistance to any country that traded in strategic materials with the Soviet Union or its allies. The act covered a wide range of materials needed for the production of weapons, and was especially focused on anything that could aid atomic weapons research and construction.

The act caused a great deal of friction, especially with the non-aligned countries. India refused to accept any American imposed limits on its trade and went ahead with shipments of thorium nitrate to China. Realizing that cutting off all aid to India would do more harm than good, Secretary of State Allen Dulles negotiated a solution.