Sedan, France in the context of "Sedan Day"

The Battle of Sedan was fought during the Franco-Prussian War from 1 to 2 September 1870. Resulting in the capture of Emperor Napoleon III and over a hundred thousand troops, it effectively decided the war in favour of Prussia and its allies, though fighting continued under a new French government.

The 130,000-strong French Army of Châlons, commanded by Marshal Patrice de MacMahon and accompanied by Napoleon III, was attempting to lift the siege of Metz, only to be caught by the Prussian Fourth Army and defeated at the Battle of Beaumont on 30 August. Commanded by Generalfeldmarschall Helmuth von Moltke and accompanied by Prussian King Wilhelm I and Prussian Chancellor Otto von Bismarck, the Fourth Army and the Prussian Third Army encircled MacMahon's army at Sedan in a battle of annihilation. Marshal MacMahon was wounded during the attacks and command passed to General Auguste-Alexandre Ducrot, until assumed by General Emmanuel Félix de Wimpffen.

The Battle of Sedan or Second Battle of Sedan (12–15 May 1940) took place in World War II during the Battle of France in 1940. It was part of the German Wehrmacht's operational plan codenamed Fall Gelb (Case Yellow) for an offensive through the hilly and forested Ardennes, to encircle the Allied armies in Belgium and north-eastern France. German Army Group A crossed the Meuse with the intention of capturing Sedan and pushing westwards towards the Channel coast, to trap the Allied forces that were advancing east into Belgium, as part of the Allied Dyle Plan.

Sedan is situated on the east bank of the Meuse. Its capture would give the Germans a base from which to take the Meuse bridges and cross the river. The German divisions could then advance across the open and undefended French countryside to the English Channel. On 12 May, Sedan was captured without resistance and the Germans defeated the French defences around Sedan on the west bank of the Meuse. German Luftwaffe bombing and low morale prevented the French defenders from destroying the bridgeheads. On 14 May, the British Royal Air Force (RAF) and the French Armée de l'Air jointly tried to destroy the bridgeheads, but the Luftwaffe prevented them from doing so. In large air battles, the Allies suffered high losses which depleted Allied bomber strength in the campaign.

The Battle of Dunkirk (french: Bataille de Dunkerque) was fought around the French port of Dunkirk (Dunkerque) during the Second World War, between the Allies and Nazi Germany. As the Allies were losing the Battle of France on the Western Front, the Battle of Dunkirk was the defence and evacuation of British and other Allied forces to Britain from 26 May to 4 June 1940.

After the Phoney War, the Battle of France began in earnest on 10 May 1940. To the east, the German Army Group B invaded the Netherlands and advanced westward. In response, the Supreme Allied Commander, French General Maurice Gamelin, initiated "Plan D" and British and French troops entered Belgium to engage the Germans in the Netherlands. French planning for war relied on the Maginot Line fortifications along the German–French border protecting the region of Lorraine but the line did not cover the Belgian border. German forces had already crossed most of the Netherlands before the French forces had arrived. Gamelin instead committed the forces under his command – three mechanized forces, the French First and Seventh Armies and the British Expeditionary Force (BEF) – to the River Dyle. On 14 May, German Army Group A burst through the Ardennes and advanced rapidly westward toward Sedan, turning northward to the English Channel, using Generalfeldmarschall Erich von Manstein's plan Sichelschnitt (under the German strategy Fall Gelb), effectively flanking the Allied forces.