Final answer:
The writers of the Constitution gave Congress a voice in most foreign policy decisions to ensure checks and balances and prevent the president from making unilateral decisions.
Step-by-step explanation:
The writers of the Constitution gave Congress a voice in most foreign policy decisions to ensure that not just one person had all the power in making these important decisions, like whether or not to go to war. This principle is known as checks and balances, which is a key aspect of the U.S. system of government. By involving Congress in foreign policy decisions, it prevents the president from making unilateral decisions without considering the input and perspectives of other branches of government.
Learn more about reasons for Congress having a voice in foreign policy decisions