Complex sentence: Osman wanted to modernize the army, which he blamed for the defeat; his plans for modernization were, however, opposed by the traditional-minded janissaries, culminating in the rebellion of janissaries in 1622, in which Osman II was deposed and killed.
Split into simpler sentences: Osman wanted to modernize the army, which he blamed for the defeat; his plans for modernization were, however, opposed by the tradition-minded janissaries. That opposition resulted in the rebellion of janissaries in 1622, in which Osman II was deposed and killed.