Answer based on context:

After the subjugation of the Livonians the crusaders turned their attention to the Latgallian principalities to the east, along the Gauja and Daugava rivers. The military alliance in 1208 and later conversion from Greek Orthodoxy to Roman Catholicism of the Principality of Tālava was the only peaceful subjugation of the Baltic tribes during the Nordic crusades. The ruler of Tālava, Tālivaldis , became the most loyal ally of German crusaders against the Estonians, and he died a Catholic martyr in 1215. The war against the Latgallian and Selonian countries along the Daugava waterway started in 1208 by occupation of the Orthodox Principality of Koknese and the Selonian Sēlpils hillfort. The campaign continued in 1209 with an attack on the Orthodox Principality of Jersika , accused by crusaders of being in alliance with Lithuanian pagans. After defeat the king of Jersika, Visvaldis, became the vassal of the Bishop of Livonia and received part of his country  as a fiefdom. The Selonian stronghold of Sēlpils was briefly the seat of a Selonian diocese , and then came under the rule of the Livonian Order . Only in 1224, with the division of Tālava and Adzele counties between the Bishop of Rīga and the Order of the Swordbearers, did Latgallian countries finally become the possession of German conquerors. The territory of the former Principality of Jersika was divided by the Bishop of Rīga and the Livonian Order in 1239.

How many years after the war against the Latgallian and Selonian countries started did Latgallian countries finally become the possession of German conquerors?
16