Complex sentence: They failed to win any major military victories or capture any major cities or fortresses, but they did blunt the effect of the Tsar's abolition of serfdom in the Russian partition, which had been designed to draw the support of peasants away from the nation.
Split into simpler sentences: They failed to win any major military victories or capture any major cities or fortresses. But they did blunt the effect of the Tsar's abolition of serfdom in the Russian partition, which had been designed to draw the support of peasants away from the nation.