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Based on this act the president can place troops into a foreign country, only needs to inform Congress within 48 hours of doing this (can be done after the fact) - Within the first 60 days, the president must receive congressional approval to keep troops in the foreign country - If Congress does not provide formal support of keeping troops in the foreign nation, the president has 30 more days to remove the troops, thus the troops can technically stay in a foreign country for a total of 90 days.
What is the War Powers Act of 1973?