De la Gardie then started to shell the Polish entrenchments near Selburg with two 12 - pounder guns , which proved quite successful ; the Polish forces of about 2,000 soldiers were caught by surprise .
A riot arose in the camp .
De la Gardie then started to shell the Polish entrenchments near Selburg with two 12 - pounder guns , which proved quite successful ; the Polish forces of about 2,000 soldiers were caught by surprise and a riot arose in the camp .