After the defeat at Vienna in 1683, the Ottoman Empire was shaken to its foundations. The Venetian Republic took advantage of this and declared war on him the following year, known as the First Morean War (1684-1699). The war brought significant changes in the area of the Cetina region and in Sinj itself, because a large part of the Dalmatian hinterland was liberated from the Ottoman rule, and this area was ruled by Venice. Immediately after coming under Venetian rule, a proposal was sent from Sinj to the friars in Rama, in the then Bosnian Sandzak, to move together with the population to the area of the Cetina region in order to get rid of the constant Ottoman persecution. Fra Pavao Vučković (1658 – 1735) agreed, and in 1687 he led the population and friars towards the Cetina region. They took with them only the necessary things and the image of Our Lady of Mercy, which will later mark the future of Sinj. A few years later, the population of Herzegovina and the Republic of Poljica settled in the Cetina region. Thus, the previously sparsely populated Cetina area finally came to life.
The relatively peaceful period enjoyed by the newly arrived population was interrupted in 1714, when the Second Morean War broke out between the Venetian Republic and the Ottoman Empire. During the war in Dalmatia, Sinj was at the center of events, which the Ottoman authorities tried at all costs to bring it back. Mustafa-pasha Čelić was appointed commander-in-chief of the Ottoman army that marched on Sinj. At the end of 1714, he gathered an army of 60,000 soldiers who were to invade Dalmatia.
Fortunately, the general providur of Dalmatia, Angelo Emo, believed that Sinj would be the first target of the Ottoman invasion. He therefore took all possible defensive measures in the form of weapons, food and logistics to better prepare the defenders for the attack. The fortress has been in extremely poor condition since the earthquake of 1709, so work to defend it had to be done quickly at least to some extent.
On the news that a huge military force was attacking them, the Venetians issued a proclamation on July 21, 1715, asking the serdars and harambashes to keep their forces on alert and stop the inhabitants fleeing towards the coast. The Venetian crew that welcomed the Ottoman forces at that time numbered just under 700 soldiers, along with about 100 other Sinj soldiers.
That the conquest of Sinj would not be easy at all, the Ottomans were convinced already in the town of Otok, where they encountered strong resistance and suffered serious losses, and several of their soldiers drowned in panic in the river Cetina. In retaliation, dozens of residents of Otok were massacred, many were taken into slavery, and those who managed to escape took refuge in the Sinj fortress. In early August, the Ottomans tightened the noose around the fort so that the Venetian crew could increasingly see their scouts gathering information on the position of the defenders and the best positions to attack. At the same time, looting raids accompanied by arson continued in the Ottoman surroundings of Sinj. Finally, on August 7, an Ottoman messenger near Sinj handed a letter to the Venetian representative requesting the unconditional surrender of the fortress, and in return the population and the army would be assured of an unhindered retreat towards the coast. The Venetians resolutely refused, so the same evening the Ottoman forces buried cannons around the fortress.
Finally, on August 8, the artillery attack on the Sinj fortress started. The defenders retaliated fiercely, so on the first day of the siege the enemy had to settle for the burning of two churches (Our Lady and St. Francis) and the destruction of houses in the part of Sinj called Varoš. The next day, the Ottomans attacked the fortress even more violently and damaged it in several places with lumbar shots and cannon balls. Despite fatigue and small numbers compared to the Ottomans, the defenders of the fortress continued to retaliate fiercely from the muskets and several cannons they possessed. After two days of violent fighting, the Ottoman forces failed to make significant progress in the direction of the fortress. On the third and fourth days of the siege, the defenders continued to repel artillery attacks and sabotage attacks by Ottoman cavalry from the wings. In parallel with the defense, the damaged parts of the fortress were repaired. The Venetian crew and the defenders of Cetina were raised by four rockets, which were fired into the air from a hill south of Sinj on August 12 by order of Providor Emme. It was a notification that they would receive help within four days in the form of the majority of Venetian forces. Even then, it was clear that the attacker would have to change tactics if he wanted to take control of the fortress as soon as possible. Attacks on the fort the next day were intensified, which was to be only an introduction to the general infantry assault. It happened as early as August 14, when Mustafa-pasha Čelić ordered an attack with all available forces.
The initial Ottoman attack was stopped just outside the fortress gates. Violent attacks and fierce clashes in front of the gates lasted for more than three hours, only to eventually be withdrawn by the Ottomans due to heavy losses. On August 15, on the feast of the Assumption, the defenders expected a new attack by Ottoman forces, but were surprised by the news that Mustafa Pasha Čelić’s army was retreating towards Livno. Thus, after a week of siege, Sinj was successfully defended.
As the main reasons for the Ottoman failure, historians cite poor logistics in the form of a small number of cannons used in the attack, then discord in the diverse military ranks and the emergence of dysentery due to poor hygiene and lack of food and water. They also see some reason for the withdrawal in the approach of Venetian auxiliary troops, which caused the Ottomans to fear that they might come into their environment. Of course, we should not forget the brave opposition of the defenders to the many times more numerous enemy.
The population of the Cetina region attributed the victory over the Ottomans to the victory and the help of the Miraculous Lady of Sinj. This opinion was shared by Providur Zorzi Balbi, who described the entire siege in his diary. The image of Our Lady was then crowned with a golden crown with a cross, made by Venetian officers by separating the money from their salaries. Apart from the Miraculous Lady of Sinj, after the victory over the Ottomans, another important element of the new identity of the population of the Cetina region became the knight’s game Sinjska alka, which has been held for more than three hundred years in memory of the magnificent victory over the Ottomans.
The siege of Sinj is a very important event in modern Croatian history. The successful defense of the city stopped the penetration of the Ottomans towards the Dalmatian coast and prevented the placing of important Venetian cities in Dalmatia, such as Split and Zadar, in an unenviable position. A more stable line of demarcation between the Ottoman Empire and the Venetian possessions was also established.