In the crusading era, there were significant Jewish communities in several cities and Jews are known to have fought alongside Arabs against the Christian invaders. During the First Crusade, Jews were among the rest of the population who tried in vain to defend Jerusalem against the Crusaders during the Siege of Jerusalem. When Jerusalem fell, a massacre of 6,000 Jews occurred when the synagogue they were seeking refuge in was set alight. Almost all perished. In Haifa, the Jewish inhabitants fought side by side with Muslims in defending the city, and held out for a whole month, (June–July 1099).