The expression “crossing the Rubicon” refers to the actions of Julius Caesar in crossing the Rubicon River and marching on Rome. Roman armies were forbidden to do so. The rule was very practical. The Romans understood the danger of allowing a large armed force to march on the capital city. To allow this might spell the end of the republic. Best that popular conquering generals and their armies stay a safe distance away and respect the democratic institutions at the heart of Roman democracy. Caesar broke the rule. He marched on Rome. He didn’t care what the Senators thought. The...