"...and just like that, four of Europe's great powers were at war. A British offer to mediate was rejected on March 8th by Paris, which published a note outlining a number of German sins. While the incursions into the Belgian Congo were listed amongst other grievances, the most immediate one was "a history of interventions in her near-abroad in the affairs and politics of other states." This "policy of unilateral intervention" left France no choice but to declare war on Germany immediately "in an effort to force the suspension of this bellicose course."
Germany, on March 10th, responded with its own note, denouncing the French for their own interventions going back decades, in not just Europe (Monaco and Serbia featuring prominently) but in Asia as well, and concluded its note with the accusation that France had conspired to violate Belgian neutrality rather than "pursue a face-saving solution for all parties involved in the Congo" and then had further put enormous pressure on Austria, mutually alliance-bound, to acquit Stephane Clement in an effort to preserve Belgian honor. The conclusions drawn in Germany's declaration of war and the subsequent evacuation of diplomatic personnel (to say nothing of businessmen and others who had stayed in France and Austria up to the last moments) essentially placed the entirety of blame for the triggering of the war in France, accusing them of manufacturing a crisis in which they used Emperor Ferdinand - a man famously skeptical of general war - as their catspaw, a fundamental understanding of the conflict that would have tremendous impact on the treatment of Austria-Hungary in the postwar compared to France and Belgium...
...Germany was mobilizing rapidly, but poor weather in the evening of March 11th led them to continue to delay their opening offensives until the 13th rather than the next day as planned; France was undeterred, and the first skirmishes of the war occurred near Dudelange in Luxembourg as French cavalry crossed the border and attacked a German border garrison, early in the morning of March 12th. This opening action was matched to the west by a Franco-Belgian attack from the direction of Arlon, seizing Steinfurt in a matter of hours as Germany declined to reinforce its border patrols and instead concentrate its mass of forces inside the Luxembourg Fortress network just beyond.
On March 13th, however, the mobilized Imperial German Army was ready to strike. Army groups were formed, with important nobles such as Bavaria's Crown Prince Rupprecht (and brother of the slain Franz) or Prussia's second prince Friedrich (selected as his elder brother, the Crown Prince Wilhelm, suffered from hemophilia) theoretically tasked in leading them by Falkenhayn. The German strategy was straightforward on paper - holding against the Franco-Belgian assault in the west, while attacking with massive force across the Bohemian and Sudetes Mountains in the East to punch into Bohemia and disrupt the Austrian industrial heartland, while also attempting to cut it off from eastern Galicia's considerable oilfields.
The third week of March saw close to a million German soldiers attack across a vast front stretching from Eger in the west to Teschen in the east. The assault was meant to seize major passes between Germany and Bohemia in order to allow a second wave of assaults through, covered by combined aerial attacks launched from rudimentary airstrips across Saxony and Silesia. The nature of the terrain into which Germany was attacking limited their ability to move motorized vehicles through, particularly landships, but it was otherwise generally thought that Germany would quickly overwhelm Austrian defenders and soon therafter engage in battles of maneuver throughout Bohemia, particularly after the Austrian offensive into Italy on March 17th convinced the Germans, wrongly, that Vienna had manpower problems.
While Eger fell late on the 14th, Germany had less luck attacking into their other sectors. While they were able to quickly seize the highlands above the Elbe near Tetschen, an attack towards Reichenberg was quickly bogged down by Austrian machine gun nests, pillboxes and other fortifications scattered around the city on both sides of the Neisse. Sixteen divisions attacked down the most natural path to cut Bohemia in half - the valley of the Morava, from the base in Glatz - but found themselves trying to invest Mahrish Schonberg as the other routes were held by Austrian troops able to rain fire down upon them from above. This "Battle of the Valleys" came to quickly and instantly show the hard limits that German offensive plans were to run up against.
Nowhere was that more obvious than in the most crucial sector of the theater, however, which was the area at Ostrau - one of the most important coal mining and steelmaking regions of Bohemia - and at Teschen, the crossroads through which Galicia could be reached from the rest of Austria without transversing the Carpathian Mountains. Ostrau lay at a point known as the Moravian Gate, a critical cauldron which Austria had correctly identified decades earlier in previous conflicts with Prussia as the most logical axis of attack in a future war, especially as industry made Ostrau ever-more critical. On March 13th, one of the great artillery and air raids against a city began, and German soldiers settled in for what would prove to be a long haul as divisions were rushed from both sides to a place soon to be synonymous with great bloodshed.
The greatest failure of the early German strike, however, was at Teschen. Time and time again, German soldiers with artillery and air support attempted to attack to seize the roads and rail that critically linked Galician defenders and oil to Ostrau, and time and time again, they were repulsed over the course of several bloody weeks. The rapid advance into Bohemia planned by German war planners had not occurred, and it was clear before long that other than the route through the mountains at Eger, the reduction of Austrian defenses along their front would take weeks, if not months, to fully penetrate to force the campaign of maneuver Falkenhayn and his general staff desired..."
- The Guns of March