The Teutonic Order actually survived after 1809, is still around today, and continued to have a military role up until the end of the First World War.

After the Order's Prussian grandmaster converted to Lutheranism and turned the Order State into a secular duchy, the Teutonic Order retreated to its lands in Germany, Austria, and Italy. The Order soon became intimately tied to the Austrians, with the later Habsburg archduke of Austria Maximilian I serving as grandmaster from 1585 and becoming archduke in 1612. In this role the Order provided 150 cavalry and 100 infantry to the Holy Roman Emperor's armies from 1593-5. From 1606 new brethren had to perform at least three years of military service on Austria's frontier against the Turks but in peacetime they could serve with the Hospitallers on Malta. Teutonic Knights were also present at the Siege of Candia in 1668 and the Siege of Vienna in 1683. Individual brethren served as commanders for the Empire and Austria, Brother Johann Caspar was minister of war to Ferdinand II from 1619-24 and Guidobald of Starhemberg fought in the Battle of Zenta in 1697.

The Teutonic Order's greatest contribution to the armies of Austria and the Empire began in 1695/6 when the Hoch- und Deutschmeister regiment was founded, whose officers were brethren of the Order, by the nineteenth century it had become Vienna's local regiment. Either as part of this regiment or serving in other posts, brethren of the Teutonic Knights fought in the War of Spanish Succession, the War of Polish Succession, the conflicts with Frederick II of Prussia, the French Revolutionary Wars, and the Napoleonic Wars. In 1809 Napoleon only managed to expel the Teutonic Order from most of the Holy Roman Empire, he did not abolish it entirely. He confiscated all their lands west of the Rhine and other German states like Saxony and Hesse took much of their remaining lands. However, the Order still survived in Austria and Italy and was very much a part of the Austrian establishment with the archdukes serving as grandmasters. In 1834 they were given sovereign status with Austria. The Hoch- und Deutschmeister regiment later fought at the Battle of Koniggratz (1866) in the Austro-Prussian War.

Though the Order had by now long had brethren who were only associate members or not vowed to celibacy, by 1914 there were still twenty professed knights, military men sworn to celibacy, poverty, and obedience, just like their medieval predecessors. These knights wore armour during their reception ceremony when they formally joined the Order, kept beards as the Order's medieval statutes required, and still wore the white mantle with a black cross. All twenty were current or former army officers. During the First World War the Order saw military service as part of the Hoch- und Deutschmeister regiment and also provided field hospitals for the Austro-Hungarian army.

It was only after Austro-Hungary's defeat in WWI that the Order finally demilitarised. The Hoch- und Deutschmeister regiment survived but was no longer officered by the Teutonic Knights and still survives today. In 1923 Archduke Eugen abdicated the grandmastership, leaving the Order's chaplains in charge. In 1929 they reformed the Order into a clerical one, finally abandoning any military pretensions. After the Anschluss in 1938 the Nazis dissolved the Teutonic Order in Austria and did the same in Czechoslovakia the following year, leaving them only with their Yugoslavian and Italian holdings. After the Second World War the Order's Austrian properties were returned.

There are still knights of honour today, men who are not professed and have no military role, but there are no longer any professed knights. The last professed Teutonic Knight was Freidrich Graf von Belrupt-Tissac, who died in 1970.

Sources:

Udo Arnold, 'Eight Hundred Years of the Teutonic Order', in Malcolm Barber (ed.), The Military Orders Volume I: Fighting for the Faith and Caring for the Sick (Aldershot, 1994), pp. 223-35.

Richard Bassett, For God and Kaiser: The Imperial Austrian Army, 1619-1918 (New Haven, 2015).

Bernhard Demel, 'Welfare and Warfare in the Teutonic Order: a Survey', Helen Nicholson (ed.), The Military Orders Vol 2: Warfare and Welfare (Aldershot, 1998), pp. 61-74.

Desmond Seward, The Monks of War (London, 2000).