Ninety-nine years ago, as the world plunged into the First World War, the experience was different. Rather than a single sharp event which plunged the world into cataclysm, there was a long series of events, at first not much noted, which in late July and early August of 1914 plunged all the major European powers into war over the course of a week.
There's a certain tendency to look, with historical hindsight, at the assassination of Archduke Ferdinand on June 28, 1914 as an incident very likely to lead to world war. There were hints of such a possibility. German Chancellor Otto von Bismark famously observed in the late 19th century that the next great European war would start with "some damn fool thing in the Balkans". When Archduke Ferdinant was assassinated, some people immediately worried that this would lead to a general war. (H. G. Wells was among those with the dubious honor of predicting a general war was coming after hearing news of the assassination on June 28th.) However, there had just been two full fledged wars in the Balkans during the last ten years, and neither had led to general war. Indeed, the great powers, for all their diplomatic entanglements, had been able to negotiate satisfactory (at least to themselves) peaces to both prior Balkan wars.
The assassination was a slow fuse. A week after the assassination, Austria-Hungary secretly sought assurances form Germany that Germany would support the Hapsburg Empire should it go to war with Serbia over the assassination. Having received these assurances (now known to history as "the blank check"), it was not until July 23rd that Austria-Hungary delivered an ultimatum to Serbia, demanding not only that Serbia hand over Serbian citizens implicated in the plot, but also that Serbia allow Austria-Hungary discretion to act within Serbia to bring to justice those responsible.
The attention of other countries was elsewhere.
The British Parliament was debating home rule for Ireland, which it was inclined to grant. In response, Unionist groups in Northern Ireland were rapidly arming, and there were serious concerns that should a rebellion in the North occur, the British army (which had a large representation of Orange men within its ranks of men and officers) would refuse to fight.
Serbia, anxious to avoid war, agreed to all but one point of Austria-Hungary's ultimatum, however Austria-Hungary (which had withdrawn its ambassador as soon as the ultimatum was delivered) was determined to put an end to Serbia's role as a regional destabilizing force and declared the concessions insufficient. Austria-Hungary declared war on Serbia on Tuesday, July 28th and immediately began bombarding the Serbian capital, Belgrade, by means of gunboats sailing on the Danube.
Russia, which had ties to Serbia, immediately ordered a partial mobilization of its army: putting its four military districts bordering Austria-Hungary on a footing of preparedness for war. It did not, however, initiate any military action against Austria-Hungary, much less Germany.
Germany was pledged to support Austria-Hungary should Russia take any military action against it. However, key leaders of the Germany military also saw responding to a Russian threat against Austria-Hungary as a way to provoke a war between Russia and Germany which they saw as inevitable, and do so before Russia's rapid industrialization and expansion of its railroads made it a more formidable enemy. On Wednesday, July 29th, in meetings of the German leadership, generals Falkenhayn and Moltke advocated war against Russia in response to Russian mobilization -- even as Kaiser Wilhelm was still conducting his famous direct telegram correspondence with the Tsar in an effort to secure peace. Further, since France had a military alliance with Russia, and France was perceived as the faster-moving power, German war plans for a war with Russia involved first attacking France and knocking it out of the war in a month-long campaign, then turning to deal with the larger, slower opponent. Thus, what the German high command was advocating was that they initiate a continent-wide war in response to a partial Russian mobilization along the Russian/Austro-Hungarian border.
In Russia, arguments were ongoing between Tsar Nicholas and his military leaders over whether it was possible to have a "partial mobilization", with the military insisting that logistical operations required that the entire army be put on a war footing. On Thursday, July 30th, Tsar Nicholas complied and ordered a general mobilization of the Russian army. On the same day Germany ordered a full mobilization of its army to commence the next day.
German mobilization, however, was not simply a matter of calling up their reservists and having troops ready at the borders. The German was plan was a detailed timetable designed to successfully prosecute a two front war against Russia and France. Thus, as German soldiers assembled and armed, the boarded trains that took them directly to the Belgian border, setting in motion an invasion of France through neutral Belgium.
On Saturday, August 1st, Germany declared war on Russia. Prepared for all eventualities, the German Ambassador delivered two copies of the declaration, one stating that Germany was declaring war because Russia had refused to respond to German demands that it stand down its armies, the other stating that Russia's response to German demands was unacceptable. That evening, France, seeing what was the wind was blowing, issued an order for immediate mobilization of its own army, including all reserves, to begin the next day, Sunday.
On that Sunday, August 2nd, Germany invaded Luxembourg, which it would use throughout the rest of the war as a staging area. That same day, The German ambassador to Belgium delivered the following communication to the Belgium's Minister for Foreign Affairs:
RELIABLE information has been received by the German Government to the effect that French forces intend to march on the line of the Meuse by Givet and Namur. This information leaves no doubt as to the intention of France to march through Belgian territory against Germany.
The German Government cannot but fear that Belgium, in spite of the utmost goodwill, will be unable, without assistance, to repel so considerable a French invasion with sufficient prospect of success to afford an adequate guarantee against danger to Germany. It is essential for the self-defence of Germany that she should anticipate any such hostile attack. The German Government would, however, feel the deepest regret if Belgium regarded as an act of hostility against herself the fact that the measures of Germany's opponents force Germany, for her own protection, to enter Belgian territory.
In order to exclude any possibility of misunderstanding, the German Government make the following declaration: --
1. Germany has in view no act of hostility against Belgium. In the event of Belgium being prepared in the coming war to maintain an attitude of friendly neutrality towards Germany, the German Government bind them selves, at the conclusion of peace, to guarantee the possessions and independence of the Belgian Kingdom in full.
2. Germany undertakes, under the above-mentioned condition, to evacuate Belgian territory on the conclusion of peace.
3. If Belgium adopts a friendly attitude, Germany is prepared, in cooperation with the Belgian authorities, to purchase all necessaries for her troops against a cash payment, and to pay an indemnity for any damage that may have been caused by German troops.
4. Should Belgium oppose the German troops, and in particular should she throw difficulties in the way of their march by a resistance of the fortresses on the Meuse, or by destroying railways, roads, tunnels, or other similar works, Germany will, to her regret, be compelled to consider Belgium as an enemy.
In this event, Germany can undertake no obligations towards Belgium, but the eventual adjustment of the relations between the two States must be left to the decision of arms.
The German Government, however, entertain the distinct hope that this eventuality will not occur, and that the Belgian Government will know how to take the necessary measures to prevent the occurrence of incidents such as those mentioned. In this case the friendly ties which bind the two neighbouring States will grow stronger and more enduring.
In 1839, all of the great powers had agreed to permanent Belgian neutrality. However, German Chancellor Bethmann Hollweg now dismissed that treaty as "a scrap of paper". King Albert of Belgium rejected the demand that German armies be allowed to pass through Belgium on their way to France.
On Monday, August 3rd, Germany formally declared war on France, it's armies already rapidly moving to attack. The next day, August 4th, one week after Austria-Hungary's declaration of war against Serbia, German soldiers crossed the Belgian frontier, opening fire on soldiers and border guards who opposed them. That same day, Britain, the last of the major powers to become involved, followed up on its commitment to defend Belgian neutrality and declared war on Germany.
The general European war had commenced.