question: What is the name of the specific lands whose plundering was achieved through temporary alliances among Lithuanian dukes that often sufficed for military ventures?
context: The Balts were largely driven to unite by external threats from aggressive German religious orders. In 1202, the Order of the Livonian Brothers of the Sword was established by Albert, the Bishop of Riga, to promote the Christianization and conquest of the Livonians, Curonians, Semigallians, and Estonians near the Gulf of Riga. The Order waged a number of successful campaigns and posed a great danger to the Lithuanian territories. The Order's progress was halted by its defeat at the Battle of Saule in 1236, after which it almost collapsed. The following year, it merged into the Teutonic Knights.In 1226, Konrad I of Masovia invited the Teutonic Knights to defend his borders and subdue the Prussians, offering the Knights the use of Chełmno (Kulm) as a base for their campaign. In 1230, they settled in Chełmno, built a castle, and began attacking Prussian lands. After 44 years, and despite two Prussian uprisings against them, they had conquered most of the Prussian tribes. Afterwards, the Knights spent nine years conquering the Nadruvians, Skalvians, and Yotvingians, and from 1283, they were better positioned to threaten the young Lithuanian state from the west.
  Further unification of the Lithuanian tribes was facilitated by the social changes that took place in Lithuania during this period. Private land ownership was established (allodiums, Lithuanian: atolai), which would later evolve into a feudal system. As attested by many chronicles, it was the principal form of organization governing land ownership in the 13th century. Under this system, known in England as primogeniture, only the eldest son could inherit lands, which allowed dukes to consolidate their holdings. Social classes and divisions of labor also began taking shape. There were classes of experienced soldiers (bajoras), of free peasants (laukininkas), and of "unfree" people (kaimynas and šeimynykštis). In order to enforce this social structure, a united state was needed. Another force behind unification was the desire to take advantage of Ruthenian lands, which were suffering from the Mongol invasion. Temporary alliances among Lithuanian dukes often sufficed for military ventures into, and plundering of, these lands (including Pskov, plundered in 1213). Altogether, between 1201 and 1236, Lithuanians launched at least 22 incursions into Livonia, 14 into Rus, and 4 into Poland. The ongoing administration of conquered territories, however, required a strong and unified central power.
answers.text: Ruthenian lands