Simon Bar Kochba was the military leader of the last great revolt of Israel against Rome (132-135 A.D.) Bar Kochba was very effective, and for several years was able to drive Rome and its legions out of Israel. Both sides suffered huge losses but for an Empire an insurrection that met with success was simply not an option. The defeat of Bar Kochba at Betar represented the last free state of Israel until the modern state of Israel was re-created in 1948.
Incidentally, the spiritual leader of this revolt was Rabbi Akiva who was illiterate until age 40. How he became one of the greatest Rabbis, respected and beloved, even in disaster, is a wonderful story in its own right.