Coalitions of the Willing refers to a group of countries that come together to take collective action, often in military or diplomatic efforts, without the explicit authorization of larger international bodies like the United Nations. This concept gained prominence in the early 21st century, especially during the U.S.-led invasion of Iraq in 2003, where several nations joined forces with the U.S. to support its objectives. These coalitions highlight the trend of unilateralism in foreign policy, where countries opt for a more flexible and less formal alliance structure to achieve their goals.