In the Middle Ages, the Székelys played a role in the defense of the Kingdom of Hungary against the Ottomans[7][8] in their posture as guards of the eastern border.

[9] In 1952, during the communist rule of Romania, the former counties with the highest concentration of Székely population – Mureș, Odorhei, Ciuc, and Trei Scaune – were legally designated as the Magyar Autonomous Region.

The Székelys were considered a distinct ethnic group (natio Siculica)[14] and formed part of the Unio Trium Nationum ("Union of Three Nations"), a coalition of three Transylvanian estates, the other two "nations" being the (also predominantly Hungarian) nobility and the Saxons (that is, ethnic German burghers).

In the Middle Ages, the Székelys played a role in the defense of the Kingdom of Hungary against the Ottomans in their posture as guards of the eastern border.

The Székelys have historically claimed descent from Attila's Huns[10] and believed they played a special role in shaping Hungary.

Ancient legends recount that a contingent of Huns remained in Transylvania, later allying with the main Hungarian army that conquered the Carpathian Basin in the 9th century.

The thirteenth-century chronicler Simon of Kéza also claimed that the Székely people descended from Huns who lived in mountainous lands prior to the Hungarian conquest.

So when they knew that the Hungarians would return to Pannonia again, they hurried to Ruthenia to them, conquering the land of Pannonia together.After the theory of Hunnic descent lost scholarly currency in the 20th century, two substantial ideas emerged about Székely ancestry:[22] Some theories suggest that the Székelys might have absorbed influences from various groups, including Turkic tribes, but this is more about cultural exchange rather than direct lineage.

The authors stated "This signal might correspond to a small genetic legacy from invasions of peoples from the Asian steppes (e.g., the Huns, Avars, and Bulgars) during the first millennium."

[29] It has boldly been noted that this is an upper limit by deep SNPs and that the main haplogroups responsible for that contribution are J2-M172 (negative M47, M67, L24, M12), J2-L24, R1a-Z93, Q-M242 and E-M78, the last of which is typically European, while N is still negligible (1.7%).

[10] The Székelys of Bukovina, today settled mostly in Vojvodina and southern Hungary, form a culturally separate group with its own history.

[34] 10 March is the anniversary of the execution in Târgu Mureș in 1854, by the Austrian authorities, of three Székelys who tried to achieve national self-determination.

Other Székely writers include the folklorist Elek Benedek, the novelist József Nyírő and the poet Sándor Kányádi.