Mieszko II Lambert (Polish pronunciation: [ˈmjɛʂkɔ ˈdruɡʲi ˈlambɛrt] ⓘ; c. 990 – 10/11 May 1034) was King of Poland from 1025 to 1031 and Duke from 1032 until his death.

He received that epithet due to the unfortunate way his reign ended, but in the beginning he acted as a skillful and talented ruler.

It is thought that the choice of this name for his son was an expression of warming relations between Bolesław I and his stepmother Oda of Haldensleben.

The real purpose of Mieszko II's visit is unclear, especially since soon afterwards, his father paid homage to the Holy Roman Empire.

Another hypothesis assumes that the territories were transferred by Bolesław to him, and as a result made Mieszko II a vassal of the Empire.

The position of the young prince, at both the Polish and Imperial courts, became stronger in 1013 when he married Richeza,[3] daughter of Count Palatine Ezzo of Lotharingia and niece of Emperor Otto III.

Probably after the wedding, and in accordance with prevailing custom, Bolesław I the Brave gave a separate district to Mieszko II to rule: Kraków.

Henry II probably wanted to force the presence of Bolesław I in Merseburg and make him explain his actions.

His army needed over a month to reach the line of the Oder River, and once there, his troops encountered strong resistance led by Mieszko II and his father.

Mieszko II refused, and after the Emperor's failure to defeat his troops in battle, Henry decided to begin retreating to Dziadoszyce.

When the Polish army advanced to Meissen, Mieszko II unsuccessfully tried to besiege the castle of his brother-in-law, Margrave Herman I (husband of his sister Regelinda).

At the same time, at the head of ten legions, Mieszko II went to Moravia and planned an allied attack together with Bohemia against the Emperor.

Due to the death of Thietmar of Merseburg, the principal chronicler of that period, there is little information about Mieszko II's life from 1018 until 1025, when he finally took over the government of Poland.

This statement was probably the result of the complete ignorance of the chronicler since in 1018, Mieszko II was 28 years old and was already fully able to exercise power by himself.

Contemporary German chroniclers considered this to be an abuse of power on the part of the Archbishop, which was made necessary by the existing political situation.

Also written was praise of the merits of Mieszko II in the building of new churches, as well his knowledge of Latin, very unusual in those times when Greek was more widely used.

In this book are found the earliest records of the Kingdom of Poland: neumes at the margins of the sequence Ad célèbres rex celica.

The devastation was so great that, according to Saxon sources, "where Mieszko II's troops put their feet grass never thence grew".

Despite the treaty which secured peace between Poland and Germany, the Emperor soon armed a retaliatory expedition against Mieszko II.

Conrad II's army arrived to Lusatia in the autumn of 1029 and began the siege of Bautzen, but the German troops did not receive the promised support of the Lutici tribe and the expedition failed.

Probably in exchange for Stephen I's support, Conrad II ceded to Hungary the territories between the Leitha and Fischa Rivers.

As a result, the Polish King lost portions of the lands taken by his father, who warred often against Emperor Henry II.

[6] Historians estimate that the reason for the rapid capitulation of Mieszko II was the bad internal situation in the country.

An additional problem was a dynastic crisis: Mieszko II's brothers continued their attempts to gain power with the help of foreign forces.

The brother who caused the first problems to Mieszko II was most likely Bezprym, who allegedly won the alliance of Kiev in order to take power with the support of Otto.

Mieszko II was not only imprisoned but also castrated, which was to be a punishment to Bolesław I the Brave, who blinded Duke Boleslaus III the Red (Oldřich's brother) thirty years before.

Having degraded the structure of power, the Duke's authority collapsed, and he was forced to send the Polish regalia to the Emperor.

After his recent opponent had regained power, the Emperor immediately reacted and began the preparations for the expedition against Poland.

[7] According to another hypothesis, Mieszko II received Greater Poland, and other neighborhoods were given to Otto and Dytryk.

Some modern historians argue that the insurrection was caused more by economic than by religious issues, such as new taxes for the Church and the militarization of the early Polish polity.