He (having taken part in the 1637 rebellion) realized that Cossacks, while having an excellent infantry, could not hope to match the Polish cavalry, which was possibly the best in Europe at the time.
他（曾参与1637年起义）意识到，具有精良步兵的哥萨克不会希望同波兰骑兵较量，这时的波兰骑兵可能是那时全欧最强的骑兵。