The Belgian response in the negative to the German ultimatum came at seven in the morning, August 3, 1914. Germany had prepared for that almost-certain outcome by training and staging a 30,000-strong strike force tasked with capturing the forts around Liege. Once that task was completed, the German invasion would begin in full.
The Belgian refusal was celebrated by the English press, though given England’s treaty obligation to defend Belgium, the refusal was tantamount to bringing England into the war:
Also on August 3rd, Germany declared war on France, followed a few hours later by France declaring war on Germany and England ordering its mobilization to begin.
Shortly after midnight on August 4, Germany launched its attack on Belgium, centered on the taking of Liege. Belgium’s army of 117,000 would fight fiercely. Germany had seven armies lined up along its borders with Belgium and France. Of these, the northernmost three were tasked to enter Belgium and pivot west and south into France. Those three armies alone consisted of 750,000 men. In contrast, Wellington’s entire army at Waterloo did not surpass 60,000 men. Each German army required enormous quantities of supplies: just the First Army needed 550 tons of food and 840 tons of fodder for its 84,000 horses per day.
Opposite the Germans, the French had deployed over one million men in five armies. France had assumed Germany would respect Belgian neutrality and had not deployed any troops on the borders with Belgium and Luxemburg. Over a week would pass before France recognized the German threat to the north and acted accordingly, though General Charles Lanzerac, commander of the northernmost French army, had expressed concern as early as July 31 about a possible German drive through Belgium. When the attack on Liege began on August 4, Lanzerac was sure it could only mean a preamble to the attack he feared. A week later, as German troops continued to mass on the Belgian border, Lanzerac again warned his superior, head of the French army General Joffre, to no avail. Only on August 14 did Joffre allow Lanzerac freedom of movement, by which point precious time had been lost.