On July 25, however, Serbia accepted Austria-Hungary’s demands almost entirely—aside from just a few conditions regarding Austria’s participation in the judicial process against the criminals. Austria-Hungary’s response was swift: its embassy in Serbia closed within a half hour of receiving Serbia’s answer, and three days later, on July 28, Austria declared war on Serbia. On July 29, the first Austrian artillery shells fell on Serbia’s capital, Belgrade.

The Other Sides Enter the War

After this first military action, a series of events followed in quick succession. With news of Austria’s attack on Belgrade, Russia ordered a general mobilization of its troops on July 30, 1914. Germany, interpreting this move as a final decision by Russia to go to war, promptly ordered its own mobilization. Although the Russian tsar and German kaiser were communicating feverishly by telegraph throughout this time, they failed to convince each other that they were only taking precautionary measures. Britain made an attempt to intervene diplomatically, but to no avail. On August 1, the German ambassador to Russia handed the Russian foreign minister a declaration of war.

On August 3, Germany, in accordance with the Schlieffen Plan (see Terms, p. 11), declared war on France as well. Germany made clear its intention to cross the neutral nation Belgium in order to reach France’s least fortified border, in violation of its own treaty in respect to neutral countries. Therefore, Britain, which had a defense agreement with Belgium, declared war on Germany the next day, August 4, bringing the number of countries involved up to six. There would soon be more.

Explaining the Start of the War

Some early accounts of World War I treat its start as a chain of almost coincidental events: a mix of unfortunate lapses in judgment on the part of political and military leaders, combined with a tangled web of alliances and defense treaties that triggered declarations of war between countries that really had little reason to be at war with each other. Although these factors were crucial, a number of other important factors were involved.

After all, most of the countries that came to be involved in World War I had enjoyed relatively friendly interrelations right up to the start of the war. For the most part, they shared strong economic interdependencies, and trade between them was brisk, making the prospect of a large-scale war highly unattractive.

Moreover, though several treaties in force at the time did compel certain countries to join the war, it is a mistake to assume that any of them joined the war “automatically.” Leaders in each country debated whether to enter the war and generally made their decisions only after evaluating their own concrete interests and risks. Many of these countries had hidden motives and, at the same time, mistakenly assumed that some of the others would stay out of the conflict.

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