A Mutual Defense Treaty is an agreement between two or more countries to provide mutual support in case one of them is attacked. This means that if one country faces aggression, the others in the treaty are obligated to assist, which can include military support or other forms of aid. Such treaties are designed to deter potential aggressors by demonstrating a united front. One of the most well-known examples of a Mutual Defense Treaty is the North Atlantic Treaty Organization (NATO) agreement, established in 1949. Under this treaty, member countries, including the United States and Canada, commit to collective defense, ensuring that an attack on one is considered an attack on all.