Yet the great quarrel between Siena and Florence in the 13th century would have probably occurred if there had been neither pope nor emperor, neither Guelf nor Ghibelline. The conflict was primarily economic. Siena at the beginning of the 13th century was the bank and trade-capital of Italy; for the freedom of trade the Sienese bankers and traders desired to keep safe the master roads to Rome, to the sea, and to the North. It was for this purpose that she made feudatories of the neighbouring lords, in an effort to associate them with her enterprise. Florence, desiring also a commercial supremacy, was Siena's natural enemy. She supported those lords who were irked by their allegiance to the city, and resisted the efforts of the Sienese to establish themselves in such key positions as Montepulciano in the south, or Poggibonsi in the north. So the history of Siena in this century is a history of futile and ulti mately hopeless wars—wars to secure the fidelity of her feuda tories, a struggle which must involve her in conflict with Florence.
In 1254 a treaty was concluded between the two cities; but three years later Florence found a pretext of war in the fact that Siena had given shelter to Ghibellines she had expelled. Siena ap pealed to Manfred for military assistance while Florence equipped a large citizen army. The first victory, though small, was Florence's, whose forces on May 18, 1260 conquered a small force outside Siena ; but on Sept. 4 the Florentines were signally defeated, and the Guelf cause for the moment lost.
Had Manfred lived the course of history might have been different : but his death, and a defeat at Benevento (1266) badly damaged the Ghibellines. The cause of the Guelfs made more and more adherents throughout Italy. Lucca, Pistoia, Volterra joined the party and the succession of Charles of Anjou to the throne of Naples added greatly to its prestige. Siena was dis heartened, too, by the death of Provenzano Salvani, who was killed in cold blood by his captor in the battle of Calle do Valdelsa (1269), and Siena's loyalty to the Ghibellines was also shaken by the growth in the city of a strong Guelf and popular party. There was war in the contado and unrest in the city, and in 1273 when Charles of Anjou visited Siena, there was nothing but sentiment left for the Ghibelline side ; Siena had lost any chance of wresting the supremacy from Florence by espousing the cause of the Guelfs. For while Siena might have gained a position of power as leader of the Ghibellines she was hopelessly outclassed by other cities when she joined the increasing party of the Guelfs.
To her wars with Florence were added internal dissensions. The rule of the nobles had become so tyrannical that in 1277 it was decreed that no patrician could occupy the chief magistracy; power was to remain in the hands of the middle-classes and traders who were adherents of the Guelfs. The size of the magistracy—which had varied from 24 to 36 members—was re duced to 15 in 1280, and seven years later to nine. This govern ment by nine merchants was successful for about 7o years, and under it Siena, while she may have lost in political importance, gained much in peace and prosperity. Florence was no longer alarmed at a possible rival, trade flourished, the university was reorganized with the help of scholars from Bologna, great build ings were constructed—indeed for this period Siena is as good an example as one could wish of a successful oligarchic plutoc racy.
In the early years of the 14th century there were many minor riots and battles, and in 1355 when the Emperor Charles IV. passed through Siena he gave his blessing to an irregular government of 1 2 which had been set up by the reformers against the nine. Power was given to the proletarians —the lower classes called ordini and monti; but they depended for not a little of their authority on the backing of the nobles. It was really a rising of the patricians and the plebeians against the tradesmen. The whole city was faction-ridden, and there is nothing but a dreary passing back of power from one set to another. Charles IV. intervened in 1368 on behalf of a re bellion; and he with Malatesta di Rimini attacked the public palace and was completely defeated by the Sienese who rallied to the call of the 15. The emperor was captured, and used his imprisonment to borrow money from Biccherna, for which he granted Siena a privilegium and appointed the magistrates im perial vicars for ever in Siena and the district. After this the new government had the usual difficulties with the dissatisfied and the unenfranchised, and took refuge in the usual device of creat ing a special police, whose chief was called esecutore, which should repress the activities of the nobles. The continuance of inter nal disorders was naturally an incentive to those forces out side the city proper. The lords, who had once been feudatories to the growing power of the Ghibelline city, threw off its yoke and were helped in their disloyalty by mercenary companies from Brittany and Gascony.