Fort Ethan Allen relied on more than its thick exterior walls for defense against enemy attack. Guards stationed outside the fort in sentry boxes checked unfamiliar wagons for valid passes before allowing entry. Inside, guards patrolled and stood watch on the parapets. In the event of a Confederate attack, a guardhouse and bombproofs allowed soldiers to take cover. Underground bunkers with heavy timber roofs protected ammunition stores within walls 12 to 18 feet thick.