World War II: The Western Allied invasion of Germany begins near the city of Aachen.

The Battle of Aachen was a combat action of World War II, fought by American and German forces in and around Aachen, Germany, between 221 October 1944. The city had been incorporated into the Siegfried Line, the main defensive network on Germany's western border; the Allies had hoped to capture it quickly and advance into the industrialized Ruhr Basin. Although most of Aachen's civilian population was evacuated before the battle began, much of the city was destroyed and both sides suffered heavy losses. It was one of the largest urban battles fought by U.S. forces in World War II, and the first city on German soil to be captured by the Allies. The battle ended with a German surrender, but their tenacious defense significantly disrupted Allied plans for the advance into Germany.

The Western Allied invasion of Germany was coordinated by the Western Allies during the final months of hostilities in the European theatre of World War II. In preparation for the Allied invasion of Germany east of the Rhine, a series of offensive operations were designed to seize and capture the east and west bank of the Rhine: Operation Veritable and Operation Grenade in February 1945, and Operation Lumberjack and Operation Undertone in March 1945, these are considered separate from the invasion of Germany proper. The Allied invasion of Germany east of the Rhine started with the Western Allies crossing the river on 22 March 1945 before fanning out and overrunning all of western Germany from the Baltic in the north to the Alpine passes in the south, where they linked up with troops of the U.S. Fifth Army in Italy. Combined with the capture of Berchtesgaden, any hope of Nazi leadership continuing to wage war from a so-called "National redoubt" or escape through the Alps was crushed, shortly followed by unconditional German surrender on 8 May 1945. This is known as the Central Europe Campaign in United States military histories.

By early 1945, events favored the Allied forces in Europe. On the Western Front the Allies had been fighting in Germany with campaigns against the Siegfried Line since the Battle of Aachen and the Battle of Hurtgen Forest in late 1944 and by January 1945 had pushed the Germans back to their starting points during the Battle of the Bulge. The failure of this offensive exhausted Germany's strategic reserve, leaving it ill-prepared to resist the final Allied campaigns in Europe. Additional losses in the Rhineland further weakened the German Army, leaving shattered remnants of units to defend the east bank of the Rhine. On 7 March, the Allies seized the last remaining intact bridge across the Rhine at Remagen, and had established a large bridgehead on the river's east bank. During Operation Lumberjack, Operation Plunder and Operation Undertone in March 1945, German casualties during February–March 1945 are estimated at 400,000 men, including 280,000 men captured as prisoners of war.On the Eastern Front, the Soviet Red Army (including the Polish Armed Forces in the East under Soviet command) simultaneously with the Western Allies, had taken most of Poland and began their offensive into Eastern Germany in February 1945, and by March were within striking distance of Berlin. The initial advance into Romania, the First Jassy–Kishinev Offensive in April and May 1944 was a failure; the Second Jassy–Kishinev Offensive in August succeeded. The Red Army also pushed deep into Hungary (the Budapest Offensive) and eastern Czechoslovakia and temporarily halted at what is now the modern Germany–Poland border on the Oder–Neisse line. These rapid advances on the Eastern Front destroyed additional veteran German combat units and severely limited German Führer Adolf Hitler's ability to reinforce his Rhine defenses. With the Western Allies making final preparations for their powerful offensive into the German heartland, victory was imminent.