The Ghassanids were the first knights’ protectors of the Holy Land under the Byzantine Empire around 500 years before the First Crusade and the creation of the first Orders of Chivalry. That makes the Ghassanid knights some of history's first, if not the very first, Christian knights.
Although not organized in Orders "per se", the Ghassanids were the first defenders of Christianity in history to incorporate what's known today as a "code of chivalry" (originated from the Arab concept of "Muru’a") which means bravery in war, hospitality, respect for women and for honor, and protection of the weak and the orphans.
The Ghassanid knights, especially as part of the Roman Empire of the East, would fight under the banner of Christ Pantocrator and Saint Sergius.
The Equestrian Order of Saint Sergius is an honor of the Sovereign Imperial and Royal House of Ghassan bestowed by merit to those who are knights and dames of the House of Ghassan already or invested in recognized orders of the House of Ghassan (ordinarily those recognized by the ICOC, Augustan Society, and Union of Byzantine Nobility).