Nachmanides was the foremost halakhist of his age. Like Maimonides before him, Nachmanides was a Spaniard who was both a physician and a great Torah scholar. However, unlike the rationalist Maimonides, Nachmanides had a strong mystical bent. His biblical commentaries are the first ones to incorporate the mystical teachings of kabbalah.
He was well-known for his aggressive refutations of Christianity, most notably, his debate with Pablo Christiani, a converted Jew, before King Jaime I of Spain in 1263.
Nachmanides could be described as one of history's first Zionists, because he declared that it is a mitzvah to take possession of Israel and to live in it (relying on Num. 33:53). He said, "So long as Israel occupies [the Holy Land], the earth is regarded as subject to Him." Nachmanides fulfilled this commandment, moving to the Holy Land during the Crusades after he was expelled from Spain for his polemics. He found devastation in the Holy Land, "but even in this destruction," he said, "it is a blessed land." He died there in 1270 C.E.
Sources: Judaism 101