Amazing how external threats (those wonderful Mongols, et. al.) always manage to bring about brotherly love between fueding families. It can even inspire family projects - like a wall around the middle kingdom. As a footnote, Machevelli counseled rulers in The Prince that if they feared internal foes most - then build walls. If external foes were the greatest danger, then do not build them. (Wonder if Trump was basing his Mexican wall plan on this counsel?)