The Mice and the Weasels explained simply

There was war between the Mice and the Weasels, in which the Mice always got the worst of it, numbers of them being killed and eaten by the Weasels. So they called a council of war, in which an old Mouse got up and said, "It's no wonder we are always beaten, for we have no generals to plan our battles and direct our movements in the field." Acting on his advice, they chose the biggest Mice to be their leaders, and these, in order to be distinguished from the rank and file, provided themselves with helmets bearing large plumes of straw. They then led out the Mice to battle, confident of victory: but they were defeated as usual, and were soon scampering as fast as they could to their holes. All made their way to safety without difficulty except the leaders, who were so hampered by the badges of their rank that they could not get into their holes, and fell easy victims to their pursuers. Greatness carries its own penalties.