The crusades did not end with the fall of the Catholic/Israelite Kingdom of Acre in 1291. Some of the more famous crusades after the 1200s include:
*]The Crusade of Nicopolis in 1396
*]The Crusade of Belgrade in 1456
*]The Crusade of Granada in 1492
*]The Crusade of Lepanto in 1571
*]The Crusade of Vienna in 1683
I also think a case could be made that there were further crusades against the Ottomans and the Barbary States in the 1700s, because some of the wars against them were funded by the pope and fought by crusader orders.
*]The Battle of Petrovaradin in 1716 should, I think, be called the Crusade of Petrovaradin. J.E. Darras describes it with crusader imagery in his book, “A General History of the Catholic Church” Volume 4 Period 8 Chapter 3:
“To every European court [Pope Clement XI] sent his legates… ‘If it becomes necessary,’ [he] said…‘I shall…[sell] every chalice and ciborium in Italy.’ At his call, Spain, Portugal, Genoa, Tuscany, the Knights of Malta, equipped their squadrons, and the combined fleet rode the waters of the archipelago under the Pontifical banner. … At the head of sixty thousand men, the [commander] Eugene [of Savoy] crushed the Turks at Peterwardein.” I’ve read that the Teutonic Knights of Austria also participated in the Crusade of Petrovaradin, because Austria intervened to assist the Venetians in their war with the Ottomans Empire. As for the Barbary states:
During the 1700s, the Knights of Malta, a crusader order, continued their occasional battles against Muslims by fighting the Barbary pirates. Not only did they patrol the Mediterranean Sea on behalf of the Catholic kingdoms of Europe, but when Catholic states went to war against Muslims states, the Knights of Malta would join the fray. Examples include:
*]The Battle of Matapan in 1717. Wikipedia says: “The naval Battle of Matapan took place…in southern Greece, between the combined naval forces of Venice, Portugal, the Papal States and Malta and the Ottoman fleet, under Kapudan Pasha Eğribozlu İbrahim.” “Pope Clement XI provid[ed] financial support and France guarantee[d] Austrian possessions in Italy.”
*]The 2nd Bombardment of Algiers in 1784. Wikipedia says: “The 2nd Bombardment of Algiers took place between 12 and 21 July 1784. A joint Spanish-Neapolitan-Maltese-Portuguese fleet commanded by the experienced Spanish Admiral Antonio Barceló bombarded the city, which was the main base of the Barbary [pirates], with the aim of forcing them to interrupt their activities.” Wikipedia even says that the expedition “was financed by Pope Pius VI…”
From my perspective, therefore, crusader orders continued to join international expeditions to fight defensive wars against Muslim attackers with papal support until the end of the 1700s. In 1798 Napoleon scattered the Order of Malta, resulting in the loss of their naval base in Malta. Then, in 1809, Napoleon abolished the Teutonic Knights in most of his empire. Some consider these dates the end of the age of the crusader orders, but they survived in other states.
Many of the Knights of Malta moved to Russia after 1798, where a branch of the Order had been created with the support of the Russian Orthodox emperor of Russia, who was a friend of the pope. In this year, 1798, Pope Pius VI called upon the Russian emperor to use those Knights to rescue him from his imprisonment by Emperor Napoleon. [Footnote 1]] I think we can consider this a call for a crusade for several reasons. One, the pope called for military action by crusader knights. Two, there was precedent for calling a crusade against an emperor – one had been called against Frederick II in the 1200s. Third, the day of Emperor Napoleon’s eventual defeat by the Russians at Waterloo was elevated to a feast day like other crusade victories as the feast of Mary, Help of Christians.
Therefore, I think we can consider the Maltese crusaders to have continued fighting for the defense of Christendom at least until 1815. The crusader spirit was still alive in 1823, when the Knights Hospitaller made an agreement with a Greek coalition fighting for freedom from Muslim rule to help them by liberating the island of Rhodes. (Encyclopedia Brittanica Volume 24, 1911, p. 18) From what I’ve read, I gather that the Greeks had specifically petitioned the pope for help against the Turks, and the planned crusader expedition was the response. Unfortunately, the plan was aborted after sufficient funds could not be raised.
Emperor Francis II of Austria was apparently interested in maintaining the Knights Hospitallers’ military services for wars against the Ottomans in the early 1800s, and offered them an island as a homeland. They didn’t accept, but he had the Teutonic Knights at his service, so maybe he used them.
The Teutonic Knights had been abolished in Napoleon’s empire in 1809, but their order continued to exist in Austria. I’m guessing they trained for military engagement with the Austrian army, because, according to this site, they only lost their military function in 1855, and they continued to assist the Austrian armies with field hospitals after that.
Many people seem to think the crusades ended in the 1200s. I think the evidence suggests that the crusading spirit continued at least into the mid-1800s, and in some ways it’s still alive today. The more you know.
 I haven’t read the following text yet, but I have a citation for Smith, Harrison, and Storace, Joseph E, Order of Saint John of Jerusalem, Second Edition, Akker Print, Delft, The Netherlands 1977, and the comment, “Pius’s letter is in part reproduced in…page 107.” I got this from a Jonathan Riley-Smith article at: orderstjohn.org/osj/sjhist2.htm