In 1303, the "good Gherardo", by now old and tired, handed over the rule of his realm to his son Rizzardo who, unfortunately, was not to prove as great a man as his father. His arrogant and equivocal politics and his unclear alliances aroused the suspicions of the Trevisan Guelph families (the Azzoni, the Collalto etc.) who took away his "ragna" (web) by having a peasant do away with him. The peasant entered the palace in St. Agostino during a feast, hitting Rizzardo, who was playing chess, on the head with a pruning-hook. The peasant himself was then also promptly killed by the same conspirators who had originally armed him, concerned with eliminating any incriminating evidence. Rizzardo died a few days later, in the arms of his wife Giovannina Visconti.
His brother Guecellone, a master of intrigue and double-crosses, succeeded him; a man so treacherous he caused a general revolt by the Trevisans. These, led by the Bishop, drove Guecellone out of the city on December 15, 1312, forcing him to flee to Serravalle in the Vittorio Veneto region. After these not so edifying experiences, Treviso no longer wanted anything to do with Lords and Esquires. Treviso's desire was to retain independence: new municipal statutes were written; new, robust fortresses built; study was encouraged and the City's best traditions returned. This desire, however, was at odds with that two powerfull and warlike families of the time: the family of Can Grande della Scala, Lord of Verona and that of Francesco il Vecchio of Carrara, lord of Padua.  
Can Grande attempted to conquer the city by valour or deception, repeatedly bringing his troops to the city walls. In this he was aided by Guecello da Camino, who was unresigned to his exile. During this time, enraged by the betrayals and connivances of several families with Can Grande, the Trevisans razed to the ground the palaces of the Da Camino, Artico Tempesta, the Ravagnini, the Morgani, the Coderta, etc. Can Grande didn't give up, however, and held the City of the Sile under constant threat from his base camp in Mogliano, roaming the area between Conegliano and Mestre with his troops. And so Treviso called Federico il Bello, Duke of Austria to its aid. Count Enrico di Gorizia was sent to govern Treviso, followed later by other vicars. Under the Imperial government the City returned to minting coins and for seven years (1319-1326) breathed the air of freedom again. This was despite the continuing rivalry and battles between the principal families (Azzoni, Camposampiero, Collalto, Tempesta) who were contending for supremacy, favouring the conquest of Treviso by Can Grande.
It was during the weak government of Guecello Tempesta begun on January 5, 1327 and which lasted about two years, that the city opened her gates to the Lord of Verona. It was a dearly bought victory, in terms of human life on both sides, and destined to end tragically just four days later with the death of Can Grande himself due it is said, to a violent intestinal colic caused by the cold fountain water drunk in abundant quantities upon entering the city.

THE DOMINION OF THE SCALIGERO FAMILY

The dominion of the Scaligero family in Treviso lasted ten years (1329-1338), with the connivance of the principal families: the Tempesta, the d'Oniqo, the di Rovero, the dalla Rocca, the da Monfumo, the da Coderta, the Barovieri of Castelfranco etc .. During their rule, the Scagligeri adapted statutes to their advantage, imposed new, heavy taxes, and repaired the medieval walls. It was also the era when the Serenissima Repubblica (The Serene Republic of Venice) was gaining territory on the mainland, occupying new lands and waging war against the Scaligeri, the Carraresi, the Gonzaga, the Visconti, the Counts of Gorizia etc .. These were long, persistent battles strewn with alternate losses and victories, connivances and "spontaneous' surrenders.
And so, in 1339, Treviso became part of the dominion of Venice, who nominated Marin Faliero (future hapless Doge) as its first Mayor, a man who set himself to healing the City's war wounds and improving its agricultural economy. Marin Faliero was so successful that on February 11, 1344, the Trevisans in a "unanimous decision by the Council of the 300, surrendered the City, its castles, treasures, regions and jurisdictions to Venice".
After many years of upheaval, the City seemed able at last, to enjoy a period of peace and prosperity, but the rumblings of war once more approached its walls following the outbreak of fighting between the Hungarian King, Ludovic the Great, and Venice for supremacy on the Adriactic. Foreign troops, invading the Veneto region, besieged Treviso on July 26, 1356 (according to A. Battistella), reinforced by the armies sent by Francesco da Carrara, who dreamed of extending his rule to the Marca. The Onigo and Collalto families and the Bishop of Ceneda also joined the enemy camp forcing Venice, beaten in the decisive battle at Nervesa on February 18, 1358, to sign the peace treaty at Zara, reclaiming Treviso but losing all the Dalmatian coast.
Another brief period of respite was enjoyed before the Venetian Republic was again at war against internal and foreign enemies. These wars also involved, directly or indirectly, the Trevisan Marca, until, abandoned by Venice (exhausted by the long conflict with the Republic of Genoa and internal defections), Treviso was "given" to Leopold, Duke of Austria. Leopold entered the City on May 8, 1381, greeted festively by the Trevisans who by now were used to putting on a brave face and making the best of things. There followed another brief period of tranquillity which lasted only three years when the Carrarese besieged Treviso anew, this time adopting a more convincing argument: sighting Ca' Foncello and firing fatal artillery broadsides from wooden towers that soon forced Duke Leopoldo to the negotiation table. The surrender of the Marca (with Feltre and Belluno) ensued, after payment of 177,000 ducats: small change, but such was the value of Treviso and its environs in those days.
The rule of the da Carrara lasted four years in the Treviso region. Francesco il Vecchio governed with a despotic rule, adapting the statutes to his politics and using officials experienced in theft. Fearing the loss of Marca lands, he fortified the occupied centres with new walls and moats, bringing loyal troops and large reserves of grain into the city.
The Trevisans however tired of the outrages and larceny and rebelled on November 30, 1388, devastating the houses of the Ghibellines and the Loan Bank. A Municipal government was reinstated with a general assembly and ten member directorate, temporarily delegated to carry out all other duties. On December 3, Treviso again joined Venice and on December 15, Francesco da Carrara sadly left the City and his castle, under escort of the Viscount troops. The troops were under the command of Jacopo dal Verme, sent by the Serene Republic with vice Mayor Querini who was sent to organise the transfer.

WITH THE "SERENISSIMA" (THE SERENE REPUBLIC OF VENICE)

But here things get unexpectedly complicated - writes Michieli - due to the desires of another powerful family of the times: that of the Visconti of Milan, whose aim was to overthrow all the minor signories of the Val Padana (Paduan valley), and thus increase its dominion from the Ticino to the Brenta rivers. And