Henry V, scion of the Frankish Salian dynasty and uncontested King of the Romans since 1106, had inherited both the Investiture Controversy and the Saxon conflict from his father Henry IV.

Upon becoming the new German monarch, Henry V had granted his associate Lothair, son of Gebhard, count of Supplinburg, the Duchy of Saxony in 1106.

In 1110 he had moved to Italy and, after negotiation failed, had captured Pope Paschal II and several cardinals to enforce his coronation as Holy Roman Emperor.

On his return from Rome, he had been immediately excommunicated by the papal legate in Germany, Cuno of Praeneste, and again by Archbishop Guy de Vienne, the later Pope Callixtus II, which encouraged the Imperial princes in their rising against the emperor—most of all the Saxon Duke Lothair of Supplinburg and Archbishop Adalbert of Mainz, Henry's longtime supporter, who after his investiture had deserted him.

Henry had entrusted the Saxon affairs to his field marshal Count Henry of Mansfeld, a Saxon noble himself.

However, though he had had Adalbert imprisoned at Trifels Castle and forced Lothair to submit himself after a court hearing at the Imperial Palace of Goslar, the smoldering Saxon conflict had broken out again in March 1113 over the succession in the Thuringian territories left by late Count Ulric II of Weimar and Orlamünde.

In order to create his own power basis, Henry had made attempts to confiscate the county as a ceased fief but had met with obstinate resistance by Ulric's heir, the Count Palatine of the Rhine Siegfried, son of the Ascanian count Adalbert II of Ballenstedt.

The insurgents gather under the lead of the Osterland count Wiprecht of Groitzsch and the Thuringian count Louis the Springer, but are repulsed by Henry's troops under Mansfeld in a battle at Warnstedt near Thale.

Wiprecht, captured and at first sentenced to death for high treason, is later reprieved, imprisoned at Trifels and divested of his possessions, which pass to the House of Mansfeld.

Emperor Henry's ruthless extension of his power in Germany has produced opposition and revolt, led from 1114 by Adalbert of Mainz and Lothair, duke of Saxony, his former ally.

Lothair had risen in arms against Henry in 1112, but had been easily quelled.

A quarrel in 1113 over the succession to the counties of Weimar and Orlamünde, however, had given occasion for a fresh outbreak on the part of Lothair, whose troops had been defeated at the Battle of Warnstadt, though the duke was soon pardoned.

Having been married at Mainz on January 7, 1114 to the twelve-year-old Matilda, daughter of Henry I of England, to whom he has been betrothed for four years, the twenty-seven-year-old emperor is confronted with a further rising, initiated by the citizens of Cologne, who are soon joined by the Saxons and others.

Henry fails to take Cologne, and his forces had been defeated on February 11, 1115, at the Battle of Welfesholz, denying Henry the power to rule Saxony.

Several nobles, including the deposed Duke Henry of Lower Lorraine and the Saxon bishop Reinhard of Halberstadt, disgusted by Henry's haughty behavior, have joined the insurgents.

Among them is Otto, the eldest son of Adalbert II, Count of Ballenstedt and Adelheid, daughter of Otto I, Margrave of Meissen.

After the death of his father-in-law, Magnus, Duke of Saxony, in 1106, Otto had inherited a significant part of Magnus' properties, and had hoped to succeed him as duke.

However, Lothar of Supplinburg had been named duke in his stead.

In 1112, after Lothar had been banned, Otto had been appointed duke of Saxony by Emperor Henry V; but in the same year, he had come into a dispute with the emperor and had been stripped of his ducal title.

He now allies himself with Lothar to help defeat Hoyer I, Count of Mansfeld, who the Emperor has named duke of Saxony.

According to the chronicles of Pegau Abbey, on February 10, 1115, the Imperial forces gathered at the Kaiserpfalz of Wallhausen and moved about forty kilometers (twenty-five miles) towards Welfesholz (today part of Gerbstedt in Saxony-Anhalt) to meet the united Saxon troops led by Duke Lothair, with first skirmish occurring already on the same evening.

The next day, Henry's commander, Hoyer of Mansfeld, launches an offensive whereby he is killed in a sword combat by the young robber knight Wiprecht II, son of the arrested Count Wiprecht of Groitzsch.

The incident decides the battle: the Saxon armies of Lothair are victorious, forcing Henry's troops to take flight.

In his twelfth-century Chronica Slavorum the Saxon chronicler Helmold describes the battle as "the largest encounter in our time".

The emperor's power to rule Saxony is denied; the Bishop of Halberstadt even refuses a Christian burial of the slain imperial troops.

In November, the Mainz citizens enforce the release of Archbishop Adalbert.

However, Henry can still rely on the loyal support of his Hohenstaufen nephews, Duke Frederick II of Swabia and his brother Conrad III.

When the emperor again moves to Italy for the inheritance of Countess Matilda of Tuscany the next year, Duke Frederick will be appointed regent, which lays the grounds for the rise of the Hohenstaufen dynasty.

East Central Europe (1120–1131 CE): Hungarian Expansion under Stephen II, Polish Consolidation under Bolesław III, and Přemyslid Stability in Bohemia

Between 1120 and 1131 CE, East Central Europe—encompassing modern-day Poland, Czechia, Slovakia, Hungary, and the eastern portions of Germany and Austria east of 10°E and north of the defined southeastern boundary—experienced further political consolidation, territorial expansion, and economic growth. Stephen II of Hungary expanded royal authority and territorial influence, particularly in the Balkans; Bolesław III Wrymouth continued to strengthen Poland’s political unity and Baltic expansion; and Bohemia, under the Přemyslid dynasty, maintained stability and regional influence within the Holy Roman Empire.

Political and Military Developments

Hungarian Expansion under Stephen II

• Stephen II (r. 1116–1131) vigorously pursued territorial expansion southward into the Balkans, launching campaigns against Byzantine territories in 1127–1129 and asserting Hungarian dominance over parts of Dalmatia and neighboring regions.

• His military efforts bolstered Hungary’s position as a regional power, strengthening its southern borders and extending its influence deeper into southeastern Europe.

Continued Polish Consolidation and Baltic Integration under Bolesław III

• Bolesław III Wrymouth (r. 1102–1138) reinforced Poland’s centralized authority and expanded into Pomerania, securing its integration through extensive missionary work and the foundation of ecclesiastical institutions.

• His continued military successes stabilized Poland’s northern frontier, facilitating increased trade and economic integration along the Baltic coast.

Stability and Dynastic Continuity in Bohemia under Vladislaus I

• Bohemia remained politically stable under Duke Vladislaus I (r. 1109–1125) and his successor Soběslav I (r. 1125–1140), solidifying Přemyslid authority and reinforcing Bohemia’s strategic relationship within the Holy Roman Empire.

• The Přemyslid rulers carefully balanced autonomy with imperial alliances, ensuring Bohemia’s political stability and regional influence.

Holy Roman Empire and Regional Diplomacy

• The reign of Holy Roman Emperor Henry V (1106–1125) and the subsequent election of Lothair III (1125–1137) maintained imperial engagement in East Central European affairs, particularly influencing dynastic alliances and regional power dynamics involving Bohemia and neighboring territories.

Economic and Technological Developments

Economic Prosperity and Trade Expansion

• Stability and territorial expansion facilitated sustained economic prosperity throughout East Central Europe. Expanded Baltic trade under Polish control, Hungarian connections with Byzantine markets, and Bohemian integration into imperial trade networks stimulated economic growth.

Agricultural Productivity and Technological Improvements

• Agricultural techniques improved further with increased adoption of the heavy plow, crop rotation, and advanced iron tools. These innovations enhanced agricultural productivity, supporting population growth and urban expansion across Poland, Hungary, and Bohemia.

Cultural and Artistic Developments

Hungarian Royal Patronage and Artistic Flourishing

• Stephen II actively supported religious and cultural institutions, promoting monastic foundations, ecclesiastical building projects, and scholarly activities, enhancing Hungary’s cultural and intellectual life.

Polish Ecclesiastical Expansion and Baltic Christianization

• Bolesław III strongly supported missionary and ecclesiastical efforts in newly acquired Pomeranian territories, establishing bishoprics and monasteries that significantly advanced Poland’s Christian and cultural identity.

Continued Bohemian Cultural Vitality under Přemyslid Patronage

• The Přemyslid rulers in Bohemia continued their patronage of monasteries, manuscript production, and architectural endeavors, reinforcing Prague’s prominence as a cultural and religious center within the Holy Roman Empire.

Settlement and Urban Development

Polish Urban and Administrative Expansion

• Major Polish cities, notably Kraków, Poznań, and newly incorporated Pomeranian settlements, expanded substantially, enhancing administrative efficiency, trade infrastructure, and fortifications.

Hungarian Urban Growth and Southern Expansion

• Stephen II oversaw significant growth in Hungarian urban centers such as Esztergom, Székesfehérvár, and Dalmatian coastal cities, strengthening administrative control and commercial vitality along Hungary’s expanding frontiers.

Bohemian Urban Stability and Growth

• Prague and other Bohemian towns remained stable and prosperous under Přemyslid governance, benefiting from continued imperial trade connections and local administrative improvements.

Social and Religious Developments

Strengthening of Ecclesiastical Structures

• Ecclesiastical institutions and Christian practices became increasingly integral to regional governance, education, and cultural identities, particularly in newly Christianized Polish territories and expanding Hungarian dioceses.

Dynastic Authority and Aristocratic Power Consolidation

• Dynastic and aristocratic structures continued to solidify, reinforcing centralized royal authority under Bolesław III in Poland, Stephen II in Hungary, and Přemyslid rulers in Bohemia. The nobility increasingly played key roles in governance, warfare, and economic development.

Long-Term Consequences and Historical Significance

The era 1120–1131 CE further strengthened East Central Europe’s medieval kingdoms. Hungarian expansion under Stephen II secured enduring regional influence, Polish territorial consolidation under Bolesław III significantly advanced northern frontier security and economic integration, and Bohemian stability under the Přemyslids reinforced regional autonomy and cultural vitality. Collectively, these developments enhanced regional political stability, economic prosperity, and cultural cohesion, deeply influencing East Central Europe’s trajectory throughout the subsequent medieval centuries.

Irnerius, at the urging of Countess Matilda of Tuscany, had begun to devote himself to the study of jurisprudence, taking the Justinian code as a guide.

After teaching jurisprudence for a short while in Rome he had returned to Bologna, where he founded a new school of jurisprudence in 1084 or 1088, which soon rivaled the law school of Ravenna.

Some jurisprudence had been taught at Bologna, before Irnerius founded his school, by Pepo and a few others, and a tradition of jurisprudence had developed at Pavia since the mid-ninth century.

He has introduced the custom of explaining the Roman law by means of glosses, which originally were meager interlinear elucidations of the text, but since the glosses were often too extensive to be inserted between the lines of the text, he had begun to write them on the margin of the page, thus being the first to introduce the marginal glosses which afterwards came into general use.

After the death of Pope Paschal II, Irnerius had defended the rights of Emperor Henry V in the papal election and upheld the legality of the election of the imperial antipope Gregory VIII.

After 1116, he appears to have held some office under the emperor.

He dies, perhaps during the reign of the emperor Lothair III, but certainly before 1140.

The imperial chancellor, the Archbishop of Mainz, views Lothair of Saxony is as a perfect replacement candidate when Henry V dies in 1125.

As an extensive landowner, Lothair brings power to the table, but he is old (slightly over fifty years of age) and has no male issue, potentially making him malleable for the nobility.

He is therefore elected king of Germany after a contentious power struggle with Frederick II, Duke of Swabia, head of the Hohenstaufen.

His election is notable in that it marks a departure from the concept of hereditary succession.

Somewhat naive concerning the complex power struggle between the papacy and the empire, Lothair also consents to several symbolic acts that will subsequently be interpreted by Rome as signaling acceptance of papal confirmation of his position.

A campaign undertaken in the same year against Bohemia ends in defeat.

Among those imprisoned by the Bohemians is Albert of Ascania, future Margrave of Brandenburg.

Sobeslav of Bohemia is first documented about 1107, when he and his elder brother Duke Bořivoj II of Bohemia were expelled by their Premyslid relative Svatopluk of Olomouc and fled to the court of their maternal cousin Duke Boleslaw III Wrymouth of Poland.

After Svatopluk was assassinated during the Battle of Głogów in 1109, Borivoj's attempts to regain the Bohemian throne failed, as in the following fratricidal war his younger brother Vladislaus I prevailed, backed by King Henry V of Germany.

Later, the brothers reconciled and Sobeslav was vested with rule at Brno and Znojmo in Moravia from 1115 until 1123, when the tensions between the brothers rose again and Sobeslav was once more expelled.

Nevertheless, as the last surviving son of Vratislaus II, Sobeslav had succeeded to the ducal throne after Duke Vladislaus' death in 1125.

From the beginning, his rule had been contested by Otto II of Olomouc, the younger brother of Svatopluk, who had gained the support not only from Vladislaus' widow Richeza of Berg but also from King Lothair III of Germany.

Junior princes, throughout the Premyslid era, will often rule all or part of Moravia from Olomouc, Brno or Znojmo, with varying degrees of autonomy from the ruler of Bohemia.

When Sobeslav decided to remove Otto II from Olomouc, the despoiled prince had looked to the German king for recourse.

Lothair III, declaring that no one could succeed to the Bohemian throne without Imperial investiture, proceeded to invade on behalf of Otto II.

This, however, is dangerous to the interests of the local nobility, and they rally around Soběslav.

The German and Moravian troops under Lothair meet on February 18, 1126, with the Bohemian forces at the Battle of Chlumec, a frontier fortress at the border with the March of Meissen (either near Chlumec or near Jílové).

Sobeslav routs and captures King Lothair, while Otto II is killed in battle.

However, the relationship between the two countries returns to the former vassal-suzerain relation, as King Lothair is released on condition of Sobeslav’s investiture with Bohemia.

One year later he had acted as regent for Germany, together with his elder brother, Frederick II of Swabia.

At the death of Henry (1125), Conrad had unsuccessfully supported Frederick for the kingship of Germany.

Frederick was placed under a ban and Conrad was deprived of Franconia and the Kingdom of Burgundy, of which he was rector.

With the support of the imperial cities, Swabia, and the Duchy of Austria, Conrad is elected antiking to the Holy Roman Emperor, Lothair II, at Nuremberg in December 1127, thus establishing the Hohenstaufen dynasty.

From Nuremberg, Conrad quickly crosses the Alps to be crowned King of Italy by Anselm V, Archbishop of Milan.