Each town looked with hatred upon its powerful rival, and the communal armies were for ever meeting in the plain by the Tiber to match their strength and see if some small portion at least of a city's domains could not be wrested from her. The bitterest and most pronounced enemies in the valley were undoubtedly Assisi and Perugia. Their feuds date back to the twelfth century; but even before the Christian era these two cities of the hills had marked each other as a foe for the one was Umbrian, the other Etruscan, and they merely continued the rivalry of their founders. It is often difficult to discover the cause of each separate war, but it may, as a general rule, be traced to Perugia's inborn love of fighting, and to her restless spirit which led her to storm each town in turn. From her eyrie she looked straight down upon half the Umbrian country, and gazing daily on so fair a land the desire for possession grew ever stronger. Many towns were forced to submit to her sway, and by the thirteenth century she was the acknowledged mistress of Umbria. It is, therefore, with surprise and admiration that we watch the undaunted struggle of Assisi against a tyrant whom she hated with a hatred quite Dantesque in its bitterness and strength. Many menacing towers were built on either side of the valley, and heralds were continually sent between the two towns with insulting messages to goad the citizens forward into battle. When Perugia was known to be preparing for an attack upon Assisi, the castles and villages around hastened to break their allegiance to the weaker city and ally themselves with the Perugian griffin. Assisi was thus often obliged to defend herself unaided against the Umbrian tyrant. When, in 1321 Perugia declared war against "this most wicked city of Assisi" whose crime consisted in having fallen under the rule of the Ghibelline party of her citizens,[7] both communes were in need of money as their bellicose habits had proved expensive. Busily, therefore, they set to work about procuring it, and in a highly characteristic manner Perugia sold her right of fishing in Thrasymene for five years, while the citizens of the Seraphic City entered by force into the sacristy of San Francesco and carried off a quantity of sacred spoils. Gold ornaments, censers, chalices, crucifixes of rare workmanship and precious stuffs, were divided into lots and sold, partly to Arezzo for 14,000 golden florins, and partly to Florence for a larger sum. Now these things did not even belong to the Franciscans, but had been carefully stored in the sacristy by the Pope and his cardinals during their last visit to the town. Great, therefore, was the wrath at the Papal Court when news came of the sacrilegious robbery, and without a moment's delay a bull of excommunication was fulminated from Avignon. For thirty-eight years Assisi lay under the heavy sentence of an interdict, and, except for the feast of the "Pardon of St.