The NATO Grand Priory of St. Sebastian – Soldier Martyr was reorganized January 20, 1990 from the Grand Priory of the NATO Reserve Officers Section which had originally been established on September 29, 1983. Both actions were sanctioned by then Prince Regent and Grand Master, H.S.H. Count f. Don Fernando Campello Pinto Pereira de Sousa de Fontes of Porto, Portugal.

LTC Joseph Anthony Esposito was the first Grand Prior of the reorganized Grand Priory but is listed as Grand Prior III. He continued to serve as Grand Prior III until 1999 at which time H.E. Richard S. Flahavan was elected Grand Prior in Athens Greece in August of 1999.

NATO Grand Priory continues as the only international Grand Priory of OSMTH. This status stems from its relationship with NATO and NATO’s two reserve officer associations. The Interallied Confederation of Reserve Officers (CIOR) and the Interallied Confederation of Medical Reserve Officers (CIOMR).

NATO Grand Priory meets annually after the close of the CIOR/CIOMR Congress meeting. Current information regarding the meetings may be found on the CIOR or CIOMR websites.