On August 5, 1914, the German army launches its assault on the city of Liege in Belgium, violating the latter country’s neutrality and beginning the first battle of World War I.

By August 4, the German 1st, 2nd and 3rd Armies—some 34 divisions of men—were in the process of aligning themselves on the right wing of the German lines, poised to move into Belgium. In total, seven German armies, with a total of 1.5 million soldiers, were being assembled along the Belgian and French frontiers, ready to put the long-held Schlieffen Plan—a sweeping advance through Belgium into France envisioned by former German Chief of Staff Alfred von Schlieffen—into practice. The 2nd Army, commanded by Field Marshal Karl von Bulow, was charged with taking the city of Liege, located at the gateway into Belgium from Germany. Built on a steep 500-foot slope rising up from the Meuse River, some 200 yards wide, and defended by 12 heavily armed forts—six on either side of the river, stretching along a 30-mile circumference—Liege was considered by many to be the most heavily fortified spot in Europe.

Bulow’s 2nd Army, numbering some 320,000 men, began its attack on Liege and its 35,000 garrison troops on August 5. Six brigades, commanded by General Otto von Emmich, were detached from the 2nd Army to form a special “Army of the Meuse” that would open the way for the rest of its comrades through Liege. Confident of an easy victory with little significant Belgian resistance, the Germans assumed Emmich’s men could topple Liege while the rest of the German troops were still assembling. In fact, the Belgians put up a valiant defense from the first moment—a struggle led by their sovereign, King Albert, who had earlier urged his subjects to fight this threat to their neutrality and independence at all costs. By the end of the day on August 5, all of Liege’s 12 fortresses remained in Belgian hands.

Liege eventually fell to the Germans on August 15, but only after they had brought up the most powerful land weapons in their arsenal, the enormous siege cannons. One type of cannon, built by the Austrian munitions firm Skoda, had a barrel measuring 12-inches (305mm); the other, manufactured by Krupps in Essen, Germany, was even more massive at 16.5 inches (420mm). Until that point, the largest guns had measured 13.5 inches and were used by the British navy; the largest on land had only measured 11 inches. The heavy shelling of Liege began on August 12; on August 15, after taking 11 of Liege’s 12 forts and exploding the walls of the 12th , Fort Loncin, with a shell, Emmich and his comrade Erich Ludendorff entered Loncin to find Liege’s commander, General Gerard Mathieu Leman, alive but unconscious. Taken prisoner by the Germans, he later wrote to King Albert from Germany, “I would gladly have given my life, but Death would not have me.” For their parts, Emmich and Ludendorff were awarded Germany’s highest military medal, the Pour la Merite cross, for their capture of Liege.

The main German advance through Belgium, towards France, began three days later, on August 18. Fearful of civilian resistance, especially from snipers, or franc-tireurs, shooting at them from hidden positions in trees and bushes, German troops from the first day in Belgium took a hard line against the native population. As early as August 5, the Germans had begun not only the shooting of ordinary civilians but the deliberate execution of Belgian priests, whom German propaganda at home insisted were encouraging franc-tireur activity. “Our advance in Belgium is certainly brutal,” wrote German Chief of Staff Helmuth von Moltke to his Austrian counterpart, Conrad von Hotzendorff, on August 5. “But we are fighting for our lives and all who get in the way must take the consequences.” In total, German troops killed 5,521 civilians in Belgium and 896 in France, earning Germany the full measure of Belgian hatred and damning it in the eyes of many foreign observers. The steadfast Belgian resistance, meanwhile, at Liege and elsewhere during the German advance, would earn the small country and its valiant king the world’s respect, and provide a shining example, and a worthy cause, to the other Allied nations then entering what would become Europe’s most devastating conflict.

READ MORE: Life in the Trenches of World War I