Following the period of the Crusades

First Crusade (1096-99). Four armies of Crusaders were formed from troops of different Western European regions, led by...

The Fall of Jerusalem. Despite deteriorating relations between the Crusaders and Byzantine leaders, the combined force...

Second Crusade (1147-49). Having achieved their goal in an unexpectedly short period of time after the First Crusade,...

Explanation:

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answer; genetics;

answer; their own memory abilities;