The complex web of alliances that developed in Europe in the lead-up to World War I was one of the key factors that contributed to the outbreak of war. The alliances were formed as a result of a desire for security and protection, but they ultimately created a situation where any conflict between two nations could quickly escalate into a much larger and more devastating conflict.

The alliance system began to take shape in the late 19th century, as nations sought to build up their military strength and secure their borders. Germany, under the leadership of Kaiser Wilhelm II, sought to establish itself as a major European power and began to build up its navy and military. This led to concerns among other European nations, particularly France and Russia, who saw Germany as a potential threat to their own security.

In response, France formed an alliance with Russia, known as the Franco-Russian Alliance, in 1894. The alliance was based on a mutual defense agreement, with each country agreeing to come to the other's aid in the event of an attack. This alliance was significant, as it effectively encircled Germany and created a balance of power in Europe.

In 1904, Britain also entered into an agreement with France, known as the Entente Cordiale. While not a formal military alliance, the agreement signaled a shift in British foreign policy towards closer cooperation with France and a distancing from Germany.

The alliance system became even more complex in the years leading up to World War I. In 1907, Britain, France, and Russia entered into an agreement known as the Triple Entente. This agreement effectively created an alliance between the three nations, with each agreeing to support the others in the event of an attack.

Meanwhile, Germany had formed its own alliance system, known as the Triple Alliance, with Austria-Hungary and Italy. This alliance was based on a mutual defense agreement, with each country agreeing to come to the aid of the others in the event of an attack.

The alliance system created a situation where any conflict between two nations could quickly escalate into a much larger and more devastating conflict. When Archduke Franz Ferdinand of Austria-Hungary was assassinated by a Serbian nationalist in June 1914, the complex web of alliances was put to the test. Austria-Hungary, supported by Germany, declared war on Serbia, which was supported by Russia. This led to a series of alliances being invoked, with France and Britain entering the conflict on the side of Russia, and Germany declaring war on France and invading Belgium.