One of the important evidence of fortress construction in the mountains is the system of fortification of Jablunkov Pass called Jablunkov Šance. It was a series of small fortifications, which were gradually built in the south-eastern part of Silesia on the border with the Kingdom of Hungary and Poland from the 16th to the beginning of the 19th century. It is now located on the territory of three countries – Czech Republic, Slovakia and Poland, in particular in the vicinity of the Jablunkov Pass (551 – 605 metres above sea level).
The main fortress of this system was the Great, or also called in the sources, Jablunkov Šance, in Mosty u Jablunkova. The number of these fortifications varied with regard to the war threat to the border; there stood about 21 fortifications in total once.
The oldest documented fortress, Old Šance in Svrčinovec, was built in 1578.
In 1621, the first reference to the construction of Great Šance fortification in Mosty u Jablunkova appeared.
The main reasons for the construction of these fortifications included the threat of war from the south, from Upper Hungary (today’s Slovakia), from where there was a threat of attacks by the Ottoman Empire and Hungarian insurgents. From about the middle of the 18th century (1740), on the contrary, the Great Šance prevented the new enemy of the Austrian monarchy, the Kingdom of Prussia, to enter Hungary. The Great Šance and other fortifications have since defended themselves against attacks from the opposite, northern direction.
Another, no less important reason for defence was the important local road, which made it possible and still allows through the Jablunkov Pass one of the most advantageous crossings of the Beskydy Mountains.
The main reasons for formation and expansion of Jablunkov fortifications included the strategic, military and communication significance of the Jablunkov Pass.
Nowadays, eight fortress relics have survived, among which the Great Šance is the best preserved one.