Syrmia (Croatian: Srijem, Serbian: ?, romanized: Srem) is a region of the southern Pannonian Plain, which lies between the Danube and Sava rivers. It is divided between Serbia and Croatia. Most of the region is flat, with the exception of the low Fru?ka gora mountain stretching along the Danube in its northern part.
Srem (Serbian Cyrillic: ?) and Srijem are used to designate the region in Serbia and Croatia respectively. Other names for the region include:
Sirmium was conquered by Romans in the first century BC and became the economic and political capital of Pannonia. In 6 AD, there was an uprising of the indigenous peoples against Roman rule. However, ten later Roman Emperors were born in Sirmium or nearby. They included Herennius Etruscus (227-251), Hostilian (230?-251), Decius Traian (249-251), Claudius II (268-270), Quintillus (270), Aurelian (270-275), Probus (276-282), Maximianus Herculius (285-310), Constantius II (337-361) and Gratian (367-383). These emperors were mostly Romanised Illyrians.
In the 6th century, Pannonia, was a province of the Byzantine Empire, and included the region of Syrmia. During that time, Byzantine rule was challenged by Ostrogoths and Gepids. In 567, Byzantine rule was fully restored, but finally collapsed during the Siege of Sirmium by Avars and Slavs (582). It remained under the Avarian rule up to the c. 800, when it same under the control of the Frankish Empire. In 827, Bulgars invade Syrmia and continued to rule after a peace treaty in 845 AD. The region was later incorporated into the Principality of Lower Pannonia, but during the 10th century it became a battleground between Hungarians, Bulgarians, and Serbs.
At the beginning of the 11th century, the ruler of Syrmia was Duke Sermon, vassal of the Bulgarian emperor Samuil. There had been Bulgar resistance to Byantine rule. This collapsed and Sermon, who refused to capitulate was captured and killed by Constantine Diogenes. A new but ultimately short lived area of governance named the Thema of Sirmium was established. It included the region of Syrmia and what is now Ma?va. In 1071, Hungarians took over the region of Syrmia, but Byzantine Empire reconquered the province after the victory over Hungarians in the Battle of Syrmia (1167). Byzantine rule ended in 1180, when Syrmia was taken again by the Hungarians.
In the 13th century, the region was controlled by the Kingdom of Hungary. On 3 March 1229, the acquisition of Syrmia was confirmed by Papal bull. Pope Gregory IX wrote, "[Margaretha] soror...regis Ungarie [acquired] terram...ulterior Sirmia". In 1231, The Duke of Syrmia was Giletus. In the 1200s, the territory around Syrmia was divided into two counties: Syrmia in the east and Vukovar in the west.
In the 13th century, between 1282 and 1316, Syrmia was ruled by Stefan Dragutin of Serbia.[unreliable source?] Initially, Dragutin was a vassal of Hungary but later ruled independently. Dragutin died in 1316, and was succeeded by his son, Stefan Vladislav II (1316-1325). In 1324, Vladislav II was defeated by Stefan Uro? III De?anski of Rascia. Lower Syrmia became the subject of dispute between the Kingdoms of Rascia and Hungary.
From 1459, the Hungarian kings endorsed the House of Brankovi? and later, the Berislavi?i Grabarski family as the titular heads of the Serbian Despotate of which Syrmia was a part. They resided in Kupinik (modern Kupinovo). The local rulers included Vuk Grgurevi? (1471 to 1485); ?or?e Brankovi? (1486 to 1496), Jovan Brankovi? (1496 to 1502), Ivani? Berislavi? (1504 to 1514), and Stjepan Berislavi? (1520 to 1535). In 1522, the last of the titular Serbian despots in Syrmia, Stjepan Berislavi?, moved to Slavonia, ahead of invading Ottoman forces. Another important local governor was Laurence of Ilok, Duke of Syrmia (1477 to 1524), who reigned over large parts of the region from Ilok.
In 1521, parts of Syrmia fell to the Ottomans and by 1538, the entire region was under Ottoman control. Between 1527 and 1530, Radoslav ?elnik ruled Syrmia as an Ottoman vassal. The area of Ottoman administration in Syrmia was known as the Sanjak of Syrmia.
In 1699, the Habsburg Monarchy took western Syrmia from the Ottomans as part of the Treaty of Karlowitz. Until the Treaty of Passarowitz at the end of the Austro-Turkish War of 1716-18, remainder of Syrmia was part of the Habsburg Military Frontier.
At the end of the Austro-Russian-Turkish War of 1735-1739, there was a migration of Albanians from the Kelmendi tribe to Srem, who were recorded as speaking Albanian as late as 1921. 
In 1848 and 1849, most of Syrmia was part of the Serbian Voivodship, a Serb autonomous region within the Austrian Empire. From 1849 and 1860, Northern Syrmia, including Ilok and Ruma were part of the Voivodship of Serbia and Tami? Banat.
On 29 October 1918, Syrmia became a part of the newly independent State of Slovenes, Croats and Serbs. On 24 November 1918, the Assembly of Syrmia proclaimed the unification of Serb-populated parts of Syrmia with the Kingdom of Serbia. However, from 1 December 1918, all of Syrmia was made a part of the Kingdom of Serbs, Croats and Slovenes.
From 1918 to 1922, Syrmia remained within the Kingdom of Serbs, Croats and Slovenes and from 1922 to 1929, Syrmia was a province (oblast). In 1929, after a new territorial division, Syrmia was divided between Danube Banovina and Drina Banovina, in the Kingdom of Yugoslavia and in 1931, it was divided between Danube Banovina and Sava Banovina. In 1939, the western part of Syrmia was included into the newly formed Banovina of Croatia.
In 1941, Syrmia was occupied by the World War II Axis powers and its entire territory was ceded to the Independent State of Croatia, a Nazi puppet state. The fascist Ustashe regime systematically murdered Serbs (as part of the Genocide of the Serbs), Jews (The Holocaust), Roma (The Porajmos), and some political dissidents. In 1945, with the creation of new borders, eastern Syrmia became part of the People's Republic of Serbia, while western Syrmia became part of the People's Republic of Croatia.
In 1991, Croatia declared its independence. Serbs in western Syrmia declared an autonomous region called the "Serbian Autonomous Region of Eastern Slavonia, Baranja and Western Syrmia". This region was one of the two Serbian autonomous regions that formed the Republic of Serbian Krajina. The autonomous regions lasted until 1995, when it was reintegrated in Croatia.
Serbian Voivodship, 1848
In 2002, the population of Syrmia in Serbia was 790,697. 668,745 (84.58%) were Serb. In 2001, the population of the Croatian Vukovar-Srijem county was 204,768. The census showed, that Croats made up 78.3% of total population, Serbs 15.5%, Hungarians 1%, Rusyns 0.9% and others.
The majority of Syrmia is located in the Srem district of the Autonomous Province of Vojvodina in Serbia. A smaller area around Novi Sad is part of the South Ba?ka district, and another smaller area around Novi Beograd, Zemun, and Sur?in belongs to the City of Belgrade. The remaining part of Syrmia is part of the Vukovar-Srijem County in Croatia.
The present international border of the region of Syrmia was drawn in 1945 by the ?ilas commission. It divided the Yugoslav constituent republic of Croatia and the Autonomous Province of Vojvodina, itself part of Serbia, within Yugoslavia.
Milovan ?ilas, a Montenegrin and then a confidante of Josip Broz Tito, drew the border according to demographic criteria, which explains why the Croatian town of Ilok on the Danube, with a Croat majority, lies east of ?id in Serbia, with a Serb majority. The border drawn in 1945 was very similar to the 1931-1939 border between the Danube Banovina and the Sava Banovina within the Kingdom of Yugoslavia.
List of cities in Syrmia (with population):
Petrovaradin, Sremska Kamenica, Sremski Karlovci and Beo?in are geographically located in Syrmia, but they are part of South Ba?ka District.
Municipalities in Serbian Syrmia:
The Syrmian villages of Ne?tin and Vizi? are part of the municipality of Ba?ka Palanka, the main part of which is in Ba?ka. Several settlements that are part of the municipality of Sremska Mitrovica are located in Syrmia in Ma?va.
Municipalities and villages in Croatian Syrmia: