Which term best describes the practice of nations forming alliances as a cause of World War I?

The practice of nations forming alliances as a cause of World War I is best described by the term "alliances." This concept highlights how countries entered into agreements and partnerships that committed them to mutual defense and support in times of conflict. The complex web of alliances in Europe prior to the war created a situation in which a conflict involving one nation could quickly involve others, as allies were bound to assist each other.

For example, the Triple Alliance consisted of Germany, Austria-Hungary, and Italy, while the Triple Entente connected France, Russia, and Great Britain. When tension escalated due to various factors, including the assassination of Archduke Franz Ferdinand, these alliances ensured that a regional conflict erupted into a full-scale world war.

Understanding alliances as a key cause provides insight into how international relationships and agreements can significantly impact the likelihood of conflict, illustrating a crucial aspect of the geopolitical landscape of the early 20th century.