Napoleon's Grande Armee crossed the Niemen on 24 June 1812 with more than four hundred thousand men aimed at Moscow. Two corps were peeled off to secure the northern flank along the Baltic. Marshal MacDonald's X Corps, a Franco-Prussian force of about thirty-two thousand, was sent into Courland and turned toward Riga. By mid-July, the Russian garrison inside Riga had grown to fourteen thousand troops, and the Russian Army of Finland under Fabian Steinheil was on its way with another ten thousand. On 7 July, at the Battle of Iecava, the Prussian general Julius von Grawert defeated a Russian force under Friedrich von Lowis of Menar in the open country southwest of Riga. The Prussian advance brought MacDonald's lead elements close enough to the city's southern suburbs that Essen, as he later admitted to friends, panicked.

Essen's order on 11 July to burn the suburbs was the kind of decision a wartime governor regrets immediately. The Moscow Forstadt and the Saint Petersburg Forstadt had grown up outside Riga's medieval walls in the eighteenth century: timber houses, merchants' yards, working-class quarters of Latvian and Russian and German residents who had nothing to do with the war. Commandant Ivan Emme oversaw the arson on Essen's instruction. The wind picked up. Within hours, the fire was burning farther and faster than any plan had called for. Most of the residents lost everything they owned. Riga, defended through five months in the end, would carry the marks of its own governor's fire long after the war was over. Essen himself, after the campaign, would die at the Baldone sulphur springs in August 1813, in circumstances that some contemporaries believed were suicide.

The siege itself, when it came, was less a siege than a five-month skirmish along the Daugava. On 19 July, sixty-seven Russian gunboats finally arrived in Riga, joining a small British squadron under Sir Thomas Byam Martin that had sailed up from the Baltic. The British and Russian warships pushed up the Lielupe River, raided Sloka and Kalnciems, and threw shells into Jelgava. The Prussians under Yorck von Wartenburg pushed back. MacDonald himself, based at Daugavpils, had 130 heavy siege cannons sitting at Pilsrundale waiting to be used; Napoleon, hoping for peace talks that never opened, told him not to rush. The war near Riga drifted through August and September into a series of small engagements: Kekava, Mesoten, Daugavgriva. On 14 October, the Russian high command had had enough of Essen's miscalculations and replaced him with the Italian-born Russian general Filippo Paulucci. By December, the Grande Armee was destroyed in the Russian winter, retreating from Moscow in catastrophe. On 8 December, MacDonald ordered the Prussians to follow. Riga had held.

What ended the campaign in the north was not a battle but a defection. As the Prussian Tenth Corps withdrew through Lithuania at the end of December, Yorck von Wartenburg met the Russians at the village of Tauroggen and signed the Convention of Tauroggen on 30 December 1812, declaring Prussian neutrality without his king's authority. Within months, Prussia would join the coalition against Napoleon. The siege of Riga had cost the city its suburbs, its trade, and a measurable share of its population's homes; the campaign had, for Russia, served its purpose by tying down a French marshal at the wrong end of the empire while the larger war was decided in the snow east of Smolensk. A monument to Barclay de Tolly, the Livonian-born Russian field marshal who commanded the army the Grande Armee was chasing, was erected in Riga in 1913, evacuated and lost at sea during the First World War, and recreated and reinstalled in 2002. It stands today in Esplanade Park, looking toward the Daugava that MacDonald never crossed.