The only 100% guaranteed method is to get the king locked into a besieged castle, then autoresolve the assault, but the isolated province with no escape route comes a clsoe second (though the game will often cheat here....). I cannot count the number of times I've chased a fleeing king over the battlefield with faster units and still been unable to catch him... and also the tightest lockdown often fails to work (triangulated spears, polearms etc).
oh, and Yoyoll - dread has no bearing whatsoever on the battlefield, only on the strategic map
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