The Great Moravian Empire was a ninth century Slavic state in central Europe that probably encompassed the territories of modern Slovakia, Moravia, Bohemia and Silesia, as well as parts of Hungary and Austria. (Given the sketchy nature of the sources for this period and locale, the precise extent of the empire remains uncertain.)
The Origins of the Great Moravian Empire
Towards the end of the eighth century, two Slavic principalities emerged on either side of the White Carpathian mountain range in central Europe; on the eastern side was the Principality of Nitra based in western and central Slovakia and to the west of the mountains, the Principality of Moravia, based in the area of what is today the southern and eastern of the Czech Republic.
By the early ninth century the Moravian principality was ruled by one Mojmír, who naturally wished to expand the territory under his control. So in the year 833 he attacked the neighbouring Principality of Nitra and drove out its ruler Pribina and united the two Slavic principalities into a single feudal state which became known as 'Greater Moravia' or the 'Great Moravian Empire'.
In addition to whatever difficulties Mojmír faced in overcoming opposition within his new territorial acquisition, his creation of a new power was seen as both a threat and a challenge by the neighbouring kingdom of the East Franks or East Francia (that is, Germany.) And whereas Mojmír it seems accepted Christianity, most of the population remained largely pagan, which attracted the attention of Frankish missionaries which was another source of friction.
Eventually in the year 846 it seems as if Louis the German, king of the East Franks conspired with Mojmír's nephew, Rastislav, to have Mojmír removed, enabling Rastislav to take his place as king.
Rastislav
Rastislav (also known as Rostislav) might well have gained power at his uncle's expense with the assistance of the Franks. but despite this, conflicts with the Eastern Frankish kingdom continued during his reign. The Franks invaded in 855 and fighting continued between Great Moravia and the Franks until the year 859, when a truce was concluded.
It was specifically to counter Frankish influence that led Rastislav to seek better relations with the Byzantine Emperor Michael III, and so in the year 863 Rastislav was happy to welcome the appearance of Byzantine missionaries, in the shape of two Greek monks and scholars and also brothers by the name of Constantinus and Methodius.
Constantinus the Philosopher better known as Cyril who was given the credit for developing the first written form of the Old Slavic language, which involved the invention of a new specifically Slavic alphabet (hence the Cyrillic alphabet). Under the influence of Constantinus and Methodius Old Slavic became the liturgical language of the Greater Moravian church and which naturally looked east towards Constantinople for religious leadership.
Naturally, Rastislav's policy of friendship with the Byzantine Empire was extremely provocative from the Franks' point of view and re-ignited the conflict with Louis the German which turned into open warfare again in 869.
Rastislav was captured and blinded by the Franks and eventually died in prison at Regensburg, thereby enabling his nephew, Svätopluk to take power. (Who by some accounts played a role in enabling the capture of Rastislav in the first place.)
Svätopluk the Great
Svätopluk or Svatopluk also known as 'Svätopluk the Great', was to prove the most notable of the kings of Greater Moravia and having concluded a peace treaty with Louis the German then began to expand the Moravian Empire, acquiring Silesia, the west of Hungary and extending his control over most of Bohemia as well. (Svätopluk was no doubt helped by the fact that Louis the German died in 876 and control over East Francia subsequently divided.)
In a reversal of Rastislav's policy he expelled the Byzantine clergy, dispensed with the Slavic liturgy and replaced it with the favoured Latin of Rome. Consequently Svätopluk was able to obtain formal recognition of his position from the Papacy, as Pope John VIII issued the bull Industriae Tuae placing the lands of the Greater Moravian Empire under papal protection.
By this means Svätopluk was able to stabilise relations with his western German neighbours and consolidate what was essentially the first Christian Slavic state in the region.
The end of the Great Moravian Empire
Svätopluk died in the year 894 and was succeeded by his son Mojmír Ias king. (Although it seems as if another son also named 'Svätopluk' had a share of power in the eastern part of the Empire and is therefore often known as Svätopluk II.)
Conflict with East Francia may well have ended but within two years Mojmír faced a new threat from the east when the nomadic Magyar tribes under their leader Árpád broke into Moravian territory. Within a decade the Great Moravian Empire began to crumble under the weight of these insurgents and collapsed completely after Mojmír II was defeated and killed at the battle of Bratislava in the year 906. (Svätopluk II fled to a monastery and took holy orders.)
The Magyars took over the "Slovien" or Slovak areas east of the Carpathians, which became part of the new Magyar kingdom of Hungary and became known as Upper Hungary for much of the medieval period.
In the west a new dynasty of rulers were able to assert themselves in Bohemia, now that the Moravian Empire was no more, first as dukes and then as kings. Both Bohemia and Hungary were eventually to end up ruled by the Habsburgs as part of their sprawling European empire and remained under their control until the final dismemberment of the Austro-Hungarian Empire at the end of World War I.
The Kings of Great Moravia
Mojmír I (830-846)
Rastislav (846-870)
Sviatopluk (870-894)
Mojmír II (894-906)
SOURCES
Cyril and Methodius Apostles of the Slavs at
http://www.omda.bg/ENGL/history/kiril&meth.html
Radio Prague's History Online at
http://archiv.radio.cz/history_96/history02.html
Which begins with the immortal words; The first inhabitants of the Czech lands were prehistoric fish
The Great Moravian Empire at
http://www.slovakia-slovakia.com/history_slovakia4.htm
The Great Moravian Empire (including map) at
http://mujweb.atlas.cz/www/historycz/main2.html