Complex sentence: At first the Swedish artillery managed to hold back the Poles who did not intend to storm Wolmar without proper siege cannons, however, on December 8th such pieces arrived and an intense bombardment of Wolmar was executed which continued in ten days.
Split into simpler sentences: At first the Swedish artillery managed to hold back the Poles who did not intend to storm Wolmar without proper siege cannons. However, on December 8th such pieces arrived and an intense bombardment of Wolmar was executed which continued for ten days.