Final answer:
The Reagan Doctrine changed US foreign policy by providing support to anti-Communist armed forces worldwide without directly deploying US troops.
Step-by-step explanation:
The Reagan Doctrine changed US foreign policy by suggesting that the United States should provide support to armed forces fighting against Communist forces worldwide. This meant that the US would provide aid to groups such as the Nicaraguan Contras and the Afghan Mujahedin, who were fighting against Communist forces in their respective countries. The Reagan Doctrine aimed to roll back the influence of Communism by supporting anti-Communist forces without directly deploying US troops.