Johann David Ludwig Graf Yorck von Wartenburg (Potsdam, 26 September 1759 – Klein-Öls, 4 October 1830) was a Prussian general at the heart of the Kingdom of Prussia’s transformation—from a French ally to a Russian ally—during the War of the Sixth Coalition. Ludwig van Beethoven composed the Yorckscher Marsch in his honour.

His surname was Yorck; the “von Wartenburg” component was an honorary battle title added as a mark of distinction. His father, David Jonathan Jark (von Gostkowski), was born in Rowe in Pomerania (today Rowy, Poland) to a Lutheran pastor and served as a captain in the army of Frederick II of Prussia. His mother was born in Potsdam, and the family hailed from a small estate in Gostkow with ancestral roots among the Kashubians of Pomerania. Born in Potsdam, Yorck changed his name from Jark to Yorck, anglicising it to resemble “York” while omitting the suffix “von Gostkowski”.

Yorck joined the Prussian army in 1772 but was dismissed seven years later for insubordination after criticising recruitment practices. He then served in the Dutch military and took part in operations in the East Indies between 1783 and 1784 as a captain. Later, he fought for the French army against the British at Cape Town. Upon returning to Prussia in 1785—following the death of Frederick II—he was reinstated. He fought in Poland in 1794 during the Kościuszko Uprising, distinguishing himself at the Battle of Szczekociny.

Five years later, Yorck began to gain recognition as a commander of a light infantry regiment, pioneering the training of skirmishers. In 1805 he was appointed commander of an infantry brigade, playing a vital role in the catastrophic Jena campaign, notably as rear-guard commander at Altenzaun. He was wounded and captured during Blücher’s last engagement at Lübeck.

After the Treaty of Tilsit, Yorck became one of the key figures in the reorganisation of the Prussian army. He served first as a major general of the Western Prussian Brigade, then as inspector general of light infantry, and eventually was appointed deputy to General Grawert, commander of the auxiliary corps which Prussia was obligated to send in support of Napoleon’s Russian campaign. Yorck, a fervent patriot, often clashed with the pro-French Grawert, who soon resigned, leaving Yorck in command.

In his march toward Riga, Yorck faced opposition from General Steingell but displayed strategic acumen in a series of engagements that pushed enemy forces back to the city. He held firm against enemy generals throughout the campaign, but soon recognised the impending collapse of Napoleon’s Grande Armée. His direct superior, Marshal MacDonald, retreated before Diebitsch’s forces, leaving Yorck isolated. As a soldier, his duty was to push forward; as a Prussian patriot, he had a greater reckoning. Amid pressure from enthusiastic young officers, Yorck made a cautious but resolute choice. On 20 December, he acted.

The armistice known as the Convention of Tauroggen, signed without royal consent, declared Prussian corps “neutral”. Though met with excitement, Yorck was initially summoned for a court-martial. Diebitsch refused to allow passage of the royal summons, and Yorck was ultimately acquitted when the Treaty of Kalisch aligned Prussia with the Allies. His decision marked a turning point in Prussian history: his seasoned troops became the nucleus of the East Prussian forces, and Yorck publicly declared war on Napoleon as their commander.