ortress and town called Doboj are placed in North Bosnia, where mountains of Balkan are gently descending to the lowlands of Panonija. This area, where rivers Spreča and Usora are entering river Bosna, is with no doubt, central part if a wider area southern from river Sava, down the valley of river Bosna. Geo-strategical importance of this area is the main reason for establishment of the fortress, from which town Doboj developed through time. Town grew up, thanking to communication knot made by three valleys. Doboj came up to a first plan in second half of 19th century, when transport was based mainly to river valleys. Only through this area, it was possible to make a crossroad for rail and road traffic. Communication is opportunity for Doboj and fortress was always its necessity. In its long lasting history, fortress on the rocky hill was not developing constantly and continuously. Risings and falls of the fortress were dictated by often, even too often, war occasions, which usually lasted longer than peace. Walls and shape of the fortress were dictated by the development of war technology, so new towers and defending walls were upgraded through time. It's been a whole century that researchers are writing about fortress and town, looking at the development and architecture, meanings, defending functions, characteristics and purpose of its buildings.

What was the shape of the first fortress?

There are few additional elements to provide us with picture of its first look. Finding fragments of baked clay mixed with wood cutting are ultimate proof that fortress has prehistorically roots.

Doboj Fortress 1808. drawing

Topography of the hill refers on the shape of the fortification object. It was placed on the west side of the head, built in the shape of an arch, facing to the west and partially to the north, so it closes the way to the head. Other sides of the hill were sharp and easy to defend and there was no need to build any walls. Down the hill was dug wide trench, 20 to 30 meters. Through that trench was a road to the valley of river Bosna. Today there is a street.
During architectural-conservatory work, small trench was dug inside the west wall which is connecting south tower with the central part of the fortress. Purpose of that was to diagnose possible damages on the foundation of the wall. Interesting details were found there. Foundation of the present wall is places in a shallow trench (10-15 cm). Its edge was not ideally straight, but it reflex nonchalance approach. At few places, remaining of soil with wood cuttings were found, probably these fragments are remaining from the original soil wall.
These shallow trenches were used to build stone walls in 13th century, where original walls had to be removed. Probably those soil walls were used until 13th century, but it is impossible to prove that.
This soil was transported to the hill and mixed with other additions (wood cuttings, reed, etc), or without them. This is typical way of building in prehistorically architecture. Old Slavs used to build this way. More precise chronology is impossible, so we have to be satisfied with archeological facts, which give us general but accurate time directions. Nearby, at the Dobor fortress, near Modriča, same stages of building were found. First is prehistorical, second is Celtic from 3rd century B.C, and third is Slavic between 9th and 13th century. In the village Skugrić, near Modriča, at the fortress Nenavište, same fragments were found, ceramics from 9th to 13th century. Same traces were found in other forts in this area. Definitely the strongest evidence of this architecture were found in a settlement Crkvina, above banks of river Usora, from 9th to 13th century, from the ornaments found inside the graveyard of this settlement. Altogether, soil forts from this area are telling us about its response to challenges of events through history. Historical events, well known from the written documents, refer to arrival of nomads from far Asia, at the end of the 9th century. They even approached north Italy, France and deep into Germany. In the beginning of 10th century it was important to defend this area where raiders had to pass through.
These soil forts were called by the same name by all Slavs; southern: grad, gradina, gradište; eastern:gorod, gorodište; western:grod, grodišce. There are some historical facts about origin of the name Doboj. There are two starting points in explaining origins of the mane Doboj. First, Do (near) is prefix to word boj (war, battle), meaning "near the battle". According to second point, Dob is a base of a word Dobro (good), meaning "good place/location" which is not rare in this area: Dobrun, Dobor, Dobrota.
In 13th century, central location was changed. From the hills above banks of river Usora, it was moved to the valley, on the rock opposite from the mouth of river Spreča. On three sides of this rock was river Bosna, so the road had to stop there. This situation was well shown at the Austrian map from 1697.

Engrave from 1697.

Road was going uphill to the fortress and it was easy to defend and control and Doboj fortress has got another important function. Main road was going from the hill through Bosna valley to settlements in Usora valley near the mouth. Settlement raised near fortress got great benefit from that road, which brings advantage over village areas. Other road was going from the fortress above Doboj to settlements in Usora valley about 3 kilometers from the mouth. There was a safe crossing over river called Bogaz, where was possible to cross even when river was high. These crossings were used through history.

What are proves that building of Doboj fortress started in 13th century?

Today, it is possible to give two strong evidence of the age of Doboj fortress. First is related to graves in area Crkvina above river Usora. Ornaments found there suggest that settlement was there from 9th, maybe even end of 8th century, to 13th century. Building of a fortress implicated building of a settlement. Migration of population to a settlement near the castle is very probable. Second evidence is a result of archeological research as well. In 1970's archeological research was conducted inside the south tower. There was a surprise at the beginning. Eight angle tower, typical for 14th and 15th century, was built on foundation of other, older, round tower. These foundations were built in early 14th century, but even more probably during 13th. After that, ceramic ornaments from late 13th century were found. So ornaments from the Crkvina graveyard and south tower reveal the age of Doboj fortress.
Architect, at that time, had task to build defense fortification on top of rocky hill. The head has triangular shape with different sides. Around these sides, 1 meter thick walls were built. At the corners, there were towers, facing south-northwest-east. Southern tower was built in a round shape, eastern as well but there was entrance, with no gate, but using ladder which was often in middle age. Northwestern tower was defending the only possible way to approach the tower, from the road. That was unsecured side of the fortress and architect was aware of that fact. As a response to that, he built one dismembered wall. Shape of that wall is unknown because through history this side of the fortress was upgraded and rebuilt many times, and it was not researched systematically. First evidence of there additional upgrades are related to beginning of 15th century. Then to written documents about big Turkish upgrade from 1490. In 13th century it was built as small or medium defense fortification with a purpose to defend from catapult attacks and was not meant to respond to great army. Its purpose was to control and protect crossroad and settlements built nearby. During 13th century area around this crossroad became important marketplace, soon after that it became small town with a market and three streets.

Later on, almost one century after, big change happened suddenly. Gun powder, Chinese invent, came to Europe and practical Europeans use it to build real cannons. At the end of 14th century they are present in Serbia and Bosnia, made in Dubrovnik, like in Italian cities where they call them Bombarda's and here they were called Lombarda's. Cannon balls could easily break walls of the fortress. It was obvious that cannon balls are lethal for Doboj fortress. Catapult projectiles flew 40-50 steps, cannon balls flew double, but one century after, they flew even more. Mountain Krnjin and the fortress on it, were higher than Doboj fortress and it was easy to destroy it. Other lack of Doboj fortress was small space at the top and it was impossible to build additional defense walls. However, new attempts were made, and so called second stage of building started. Additional building was done on the northwest side, but we are not familiar with what or how was built because no detailed research was conducted. Same thing happened with the wall connecting south tower with northwest part of the fortress, this wall got another layer. In the back of northwest corner was built another rectangle tower. We know for sure it was built in the middle of 15th century. It was quite high and belonged to donjon type of towers like in Zvornik, Jajce and nearby Tešanj.

Oldest written document in history of Doboj fortress

Their purpose was to have storage for gun powder, several floors with loopholes, shelters, bastions, etc. Since Doboj fortress had towers with loopholes, donjon was built behind them and was the last line of defense.

"…in Uxora suptus castrum Doboy…- In Usora under Doboj Fortress", 16th of June 1415, in the campus of Hungarian army. This was the news from Dubrovnik merchants to Hungarian king Sigismund, and the oldest written document in history of Doboj fortress. Town was not mentioned in this document.

Results of the latest researches of old Turkish registers, provide us with extremely valuable and interesting data about Doboj town and the fortress. With the fall of the Bosnian medieval state in 1463, Turkish Empire didn't occupy areas north from Vranduk Mountain, but agreed on making a unique Bosnian kingdom. Soon after that, during summer 1476 they took over this area, including Doboj fortress, without fight. This was registered in Turkish register for 1468/69 with additions from 10th of September 1477. It was noted that dukes Jovašin and Stjepan have surrender Doboj. It is obvious that these men were commanders of Doboj guards-soldiers at the fortress in the summer 1476 when Bosnian kingdom was finished on this side of Vranduk Mountain. As a reward for this surrender with no fight, they got to rule small regions, with an obligation of military service.
From the same source, we got information about reconstruction of Doboj fortress in summer 1490. In a short time, because border with Hungary was at the fortress, great work was done. In 50 days, 1.500 builders completely reconstructed the fortress lead by architect Ibrahim.
As the demolition power of cannon balls was greater, defensive power of walls was weaker. Turks were aware of that, so architect Ibrahim came up with a solution, the only possible at that moment. He strengthened northwestern corner and encircled whole fortress with a new wall. He protected new entrances by building new tower on the east side next to the old entrance tower. New tower had passage beneath and on top there was observatory.
Doboj fortress lost its importance during 16th century because Turkish Empire reached city of Budim (1543). Since then Doboj fortress was not repaired and it was easily collapsing. In 1657, fortress had 35 guard, one small and one big cannon, five barrels of gun powder, and few cannon balls.
Doboj town and the fortress were burnt down in 1697. In a quick march from Brod to Sarajevo, Austrian duke came to Doboj. Fortress gave up after two days, and three artillery shots. Austrians were holding Doboj until 3rd of August 1700. Then they released prisoners. Austrian army burnt down town again in 1717, but fortress was not conquered. Town had approximately 50 houses.
The fortress was abandoned by army in 1851. Old fortress established in 13th century (not counting one established in 10th century) was so peaceful and lost its role in the history. Turks didn't repair fortress since the end of 15th century. That turned towers and walls into ruins. After 1851, the fortress became quarry and people took stone of it to build houses.
There is interesting description of English archeologist and journalist Arthur Evans who wrote:
"…after passing a twist on the road, on the cone hill. in front of us appeared well installed old town Doboj…
The old fortress crowns the top of the hill and we headed up there. People here cal it "old town" and it is one of the most interesting relics of whole Bosnia. One view from those ruins reveals the importance of that position. Doboj fortress is sitting on top of the hill which is falling into Bosna valley, right where Spreča River is opening the way to Drina River.
…The fortress was the key to whole Bosna valley, key against enemy who would arrive from Hungarian lowlands, and controlled main road through Usora valley down to the heart of Bosnian kingdom.
…Under Turkish occupation fortress started to collapse and now it is in ruins."
Nowadays, Doboj fortress is cultural and historical monument of a high value. Also, its silhouette is mark of a modern Doboj.