The Livonian Order used their alliance with Mindaugas to gain control over Samogitian lands.
In 1252 he approved the Order's construction of Klaipeda Castle.
Their governance, however, was seen as oppressive.
Local merchants could only conduct transactions via Order-approved intermediaries; inheritance laws were changed; and the choices among marriage partners and residencies were restricted.
Several pitched battles ensued.
In 1259 the Order lost the Battle of Skuodas, and in 1260 it lost the Battle of Durbe.
The first defeat encouraged a rebellion by the Semigalians, and the defeat at Durbe spurred the Prussians into the Great Prussian Rebellion, which lasted for 14 years.
Encouraged by these developments and by his nephew Treniota, Mindaugas broke peace with the Order.
The gains he had expected from Christianization had proven to be minor.

Mindaugas may have reverted to paganism afterwards.
His motivation for conversion is often described by modern historians as merely strategic.
The case for his apostasy rests largely on two near-contemporary sources: a 1324 assertion by Pope John XXII that Mindaugas had returned to error, and the Galician–Volhynian Chronicle.
The chronicler writes that Mindaugas continued to practice paganism, making sacrifices to his gods, burning corpses, and conducting pagan rites in public.
Historians have pointed to the possibility of bias in this account, since Mindaugas had been at war with Volhynia.
Pope Clement IV, on the other hand, wrote in 1268 of "Mindaugas of happy memory" (clare memorie Mindota), expressing regret at his murder.

In any event, the Lithuanians were not prepared to accept Christianity, and Mindaugas's baptism had little impact on further developments.
The majority of the population and the nobility remained pagan; his subjects were not required to convert.
The cathedral he had built in Vilnius was superseded by a pagan temple, and all the diplomatic achievements made after his coronation were lost, although the practice of Christianity and intermarriage were well tolerated.

Regional conflicts with the Order escalated.
Alexander Nevsky of Novgorod, Tautvilas, and Tautvilas's son Constantine agreed to form a coalition in opposition to Mindaugas, but their plans were unsuccessful.
Treniota emerged as the leader of the Samogitian resistance; he led an army to Cēsis (now in Latvia), reaching the Estonian coast, and battled Masovia (now in Poland).
His goal was to encourage all the conquered Baltic tribes to rise up against the Christian orders and unite under Lithuanian leadership.
His personal influence grew while Mindaugas was concentrating on the conquest of Ruthenian lands, dispatching a large army to Bryansk.
Treniota and Mindaugas began to pursue different priorities.
The Rhymed Chronicle mentions Mindaugas's displeasure at the fact that Treniota did not create any alliances in Latvia or Estonia; he may have come to prefer diplomacy.
In the midst of these events his wife Morta died, and Mindaugas took her sister as his new wife.
The only problem was that the sister was already married to Daumantas.
In retaliation, Daumantas and Treniota assassinated Mindaugas and two of his sons in fall 1263.
According to a late medieval tradition, the assassination took place in Aglona.
He was buried along with his horses, in accordance with ancestral tradition.
After Mindaugas's death, Lithuania lapsed into internal disorder.
Three of his successors—Treniota, his son-in-law Svarn, and his son Vaišvilkas—were assassinated during the next seven years.
Stability did not return until the reign of Traidenis, designated Grand Duke c. 1270.
The Livonian Order used their alliance with Mindaugas to gain control over Samogitian lands. In 1252 he approved the Order's construction of Klaipeda Castle. Their governance, however, was seen as oppressive. Local merchants could only conduct transactions via Order-approved intermediaries; inheritance laws were changed; and the choices among marriage partners and residencies were restricted. Several pitched battles ensued. In 1259 the Order lost the Battle of Skuodas, and in 1260 it lost the Battle of Durbe. The first defeat encouraged a rebellion by the Semigalians, and the defeat at Durbe spurred the Prussians into the Great Prussian Rebellion, which lasted for 14 years. Encouraged by these developments and by his nephew Treniota, Mindaugas broke peace with the Order. The gains he had expected from Christianization had proven to be minor.
Mindaugas may have reverted to paganism afterwards. His motivation for conversion is often described by modern historians as merely strategic. The case for his apostasy rests largely on two near-contemporary sources: a 1324 assertion by Pope John XXII that Mindaugas had returned to error, and the Galician–Volhynian Chronicle. The chronicler writes that Mindaugas continued to practice paganism, making sacrifices to his gods, burning corpses, and conducting pagan rites in public. Historians have pointed to the possibility of bias in this account, since Mindaugas had been at war with Volhynia. Pope Clement IV, on the other hand, wrote in 1268 of "Mindaugas of happy memory" (clare memorie Mindota), expressing regret at his murder.
In any event, the Lithuanians were not prepared to accept Christianity, and Mindaugas's baptism had little impact on further developments. The majority of the population and the nobility remained pagan; his subjects were not required to convert. The cathedral he had built in Vilnius was superseded by a pagan temple, and all the diplomatic achievements made after his coronation were lost, although the practice of Christianity and intermarriage were well tolerated.
Regional conflicts with the Order escalated. Alexander Nevsky of Novgorod, Tautvilas, and Tautvilas's son Constantine agreed to form a coalition in opposition to Mindaugas, but their plans were unsuccessful. Treniota emerged as the leader of the Samogitian resistance; he led an army to Cēsis (now in Latvia), reaching the Estonian coast, and battled Masovia (now in Poland). His goal was to encourage all the conquered Baltic tribes to rise up against the Christian orders and unite under Lithuanian leadership. His personal influence grew while Mindaugas was concentrating on the conquest of Ruthenian lands, dispatching a large army to Bryansk. Treniota and Mindaugas began to pursue different priorities. The Rhymed Chronicle mentions Mindaugas's displeasure at the fact that Treniota did not create any alliances in Latvia or Estonia; he may have come to prefer diplomacy. In the midst of these events his wife Morta died, and Mindaugas took her sister as his new wife. The only problem was that the sister was already married to Daumantas. In retaliation, Daumantas and Treniota assassinated Mindaugas and two of his sons in fall 1263. According to a late medieval tradition, the assassination took place in Aglona. He was buried along with his horses, in accordance with ancestral tradition. After Mindaugas's death, Lithuania lapsed into internal disorder. Three of his successors—Treniota, his son-in-law Svarn, and his son Vaišvilkas—were assassinated during the next seven years. Stability did not return until the reign of Traidenis, designated Grand Duke c. 1270.
Mindaugas