Jaromir was the second son of Boleslaus II the Pious and Emma. In 1003, he rebelled against his elder brother Boleslaus III

Boleslaus III of Bohemia

Boleslaus III , called the Red or the Blind, was the duke of Bohemia from 999 until 1002 AD. He was the "worst of all men who ever sat on the Bohemian throne."...

, who had him emasculated, but was unable to secure the throne which was subsequently taken by Boleslaw the Brave, King of Poland. Jaromir and his brother Oldrich then sought military backing from the German King Henry II

Henry II, Holy Roman Emperor

Henry II , also referred to as Saint Henry, Obl.S.B., was the fifth and last Holy Roman Emperor of the Ottonian dynasty, from his coronation in Rome in 1014 until his death a decade later. He was crowned King of the Germans in 1002 and King of Italy in 1004...

. At Merseburg

Merseburg

Merseburg is a town in the south of the German state of Saxony-Anhalt on the river Saale, approx. 14 km south of Halle . It is the capital of the Saalekreis district. It had a diocese founded by Archbishop Adalbert of Magdeburg....

, Jaromir promised to hold Bohemia

Bohemia

Bohemia is a historical region in central Europe, occupying the western two-thirds of the traditional Czech Lands. It is located in the contemporary Czech Republic with its capital in Prague...

 as a vassal of Henry. This action definitively placed Bohemia within the jurisdiction of the Holy Roman Empire

Holy Roman Empire

The Holy Roman Empire was a realm that existed from 962 to 1806 in Central Europe.It was ruled by the Holy Roman Emperor. Its character changed during the Middle Ages and the Early Modern period, when the power of the emperor gradually weakened in favour of the princes...

.

In 1004, Jaromir occupied Prague

Prague

Prague is the capital and largest city of the Czech Republic. Situated in the north-west of the country on the Vltava river, the city is home to about 1.3 million people, while its metropolitan area is estimated to have a population of over 2.3 million...

 with a German army and made himself Duke

Duke

A duke or duchess is a member of the nobility, historically of highest rank below the monarch, and historically controlling a duchy...

. The state he regained was a small one, as Polish forces still held Moravia

Moravia

Moravia is a historical region in Central Europe in the east of the Czech Republic, and one of the former Czech lands, together with Bohemia and Silesia. It takes its name from the Morava River which rises in the northwest of the region...

, Silesia

Silesia

Silesia is a historical region of Central Europe located mostly in Poland, with smaller parts also in the Czech Republic, and Germany.Silesia is rich in mineral and natural resources, and includes several important industrial areas. Silesia's largest city and historical capital is Wrocław...

, and Lusatia

Lusatia

Lusatia is a historical region in Central Europe. It stretches from the Bóbr and Kwisa rivers in the east to the Elbe valley in the west, today located within the German states of Saxony and Brandenburg as well as in the Lower Silesian and Lubusz voivodeships of western Poland...

. Jaromir's reign—like so many of the other early Czech rulers—was a struggle to regain the lost lands. In 1012, Jaromir was dethroned by Oldrich, and forced once again into exile. In a surprise campaign, Jaromir in turn managed to depose Oldrich (1033) but his second reign was short-lived. A year later Oldřich was restored by his son Bretislaus I

Bretislaus I of Bohemia

Bretislaus I , known as Bohemian Achilles, of the house of the Přemyslids, was the duke of Bohemia from 1035 till death.-Youth:...

. Jaromir was imprisoned at Lysa and died (assassinated by one from the Vršovci) in 1035, a year after his brother.