Military alliances during the 20th century had significant impacts on global politics, particularly evidenced by coalitions formed during the World Wars and the Cold War. Alliances such as NATO and the Warsaw Pact greatly influenced military and diplomatic strategies, creating a dichotomy between East and West during the Cold War. These alliances not only shaped military engagements but also imposed a framework for economic and ideological competition. They facilitated cooperative security measures among allied nations, while also fostering tensions between opposing blocs, leading to an arms race and various proxy wars that defined international relations throughout the century.