Konrad, the Polish duke of Mazovia, hopes to strengthen Polish Latin-rite Christianity and Poland’s position in regard to its neighbors.

Konrad is the youngest son of High Duke Casimir II the Just of Poland and Helen of Znojmo, daughter of the Přemyslid duke Konrad II of Znojmo (ruler of the Znojmo Appanage in southern Moravia, part of Duchy of Bohemia).

His maternal grandmother was Maria of Serbia, apparently a daughter of the pre-Nemanjić župan Uroš I of Rascia.

After his father's death in 1194, Konrad had been brought up by his mother, who had acted as regent of Masovia.

He had received Masovia in 1199 and in 1205 also the adjacent lands of Kuyavia.

In that year, he and his brother, Duke Leszek I the White of Sandomierz, had had their greatest military victory at the Battle of Zawichost against Prince Roman the Great of Galicia–Volhynia.

The Ruthenian army had been crushed and Roman had been killed in battle.

The Rurik princess Agafia of Rus became his wife.

In order to enlarge his dominions, Konrad had unsuccessfully attempted to conquer the adjacent pagan lands of Chelmno in Prussia during a 1209 crusade with the consent of Pope Innocent III.

The monk Christian of Oliva had in 1215 been appointed a missionary bishop among the Old Prussians; his residence at Chelmno had been devastated by Prussian forces the next year.

Several further campaigns in 1219 and 1222 had failed, involving Konrad in a long-term border quarrel with the Prussian tribes.

The duke's ongoing attempts on Prussia have been answered by incursions across the borders of his Masovian lands, while Prussians are in the process of gaining back control over the disputed Chelmno Land and even threaten Konrad's residence at Plock Castle.

Subjected to constant Prussian raids and counter-raids, Konrad now wants to stabilize the north of his Duchy of Masovia in this fight over the border area of Chełmno.

Thus in 1226, Konrad, having difficulty with constant raids over his territory, invites the religious military order of the Teutonic Knights to fight the Prussians, as they already had supported the Kingdom of Hungary against the Cuman people in the Transylavanian Burzenland from 1211 to 1225.

When the Knights notified Hungary that the Order was firstly responsible to the pope, they had been expelled by the Hungarian king Andrew II.

Thus, in return for the Order's service, Grand Master Hermann von Salza wants to have its rights documented beforehand, by a deal with Konrad that is to be confirmed by the Holy Roman Emperor and the Roman Curia.

Konrad I, Duke of Masovia in northeastern Poland, had in 1226, appealed to the Knights to defend his borders and subdue the pagan Baltic Prussians, allowing the Teutonic Knights use of Chelmno Land (Culmerland) as a base for their campaign.

This being a time of widespread crusading fervor throughout Western Europe, Hermann von Salza, grand master of the Teutonic Knights from 1210, had considered Prussia a good training ground for his knights for the wars against the Muslims in Outremer.

Accepting the invitation to settle, the Teutonic knights have moved north and established a stronghold at Thorn (Torun) on the Vistula River in northwestern Poland and begun the conquest and forced Christianization of the pagan Prussians to the east.

With the Golden Bull of Rimini, Emperor Frederick II had bestowed on the Order a special imperial privilege for the conquest and possession of Prussia, including Chelmno Land, with nominal papal sovereignty.

In 1235, the Teutonic Knights had assimilated the smaller Order of Dobrzyń, which had been established earlier by Christian, the first Bishop of Prussia.

Under von Salza’s leadership, the order has begun to carve out for itself the military-monastic state of Prussia, currently peopled by the original Prussians, pagan peoples who have thus far resisted outside control.

Hermann's subsequent visits with the Pope or the Emperor have brought new privileges and donations to the Order.

He was also able to obtain the incorporation of the Livonian Brothers of the Sword into the Teutonic Order in 1237.

Within the Teutonic Order, however, the knights had begun to grow dissatisfied at the absence of their Grand Master, so they had recalled him and had him withdraw from his political life.

However, he is less successful as a religious leader, and soon retired in 1238 to Salerno in 1238, where he dies the following year.

The importance of Hermann's role as mediator between Pope Gregory IX and the emperor can be seen by the fact that all communication between Frederick and the pope breaks off with Hermann's death.

At Salza’s death in 1239, the Poles attempt unsuccessfully to assert their claim to suzerainty over the Knights, who continue carving their state from the territory of the Prussians.

Poland has divided by 1240 into four states, each under the control of the Piast family.

Kraków’s King Boleslaw V is legally the preeminent ruler, but his cousin Duke Henry II of Silesia is the preeminent lord.

Duke Konrad of Mazovia, failing to grasp the danger of the Knights’ presence, had at first supported the Knights against Pomerania, but eventually shifts his alliance.