He led guerrilla warfare against Swedish troops of Charles X, a type of a campaign he authored, despite the objections of the hetmans, who by that time returned to serve under John Casmimir Vasa. The mobile Swedish forces, even with their significant firepower, proved to be rather vulnerable to Czarniecki's guerrilla-style warfare. Czarniecki was defeated at the battle of Gołąb in mid-February 1656, but later inflicted serious defeats upon the Swedes, notably at the Battle of Warka in April that year. The tide of the war turned several times that year, and he was again defeated at the battle of Kłecko and battle of Kscynia. His defeats, however, were limited, and in most cases he was able to retreat with most of his army in good order. Under his direction the popular rising against the Swedish troops in Greater Poland proved highly successful. It was against his advice that the battle of Warsaw was fought, and his subsequent strategy neutralized the ill effects of this defeat. Despite support from the king, Czarniecki was seen by many older, established noble family as an arrogant newcomer, and they prevented him from getting the hetman office that year; instead early next year he received the office of the voivode of Ruthenia, and an extraordinary title of the "general and vice commander of the royal forces", which put him in a position of an unofficial hetman-like authority. The Field Crown Hetmanship went to Jerzy Sebastian Lubomirski, also an accomplished commander, if not so much as Czarniecki – but from a magnate Lubomirski family; Czarniecki commented famously that "Not of salt, or fields, I am, but from what hurts me", alluding to the fact that Lubormirski family built its fortune on salt trade and agriculture, whereas his smaller one was built through military service – yet it was money and politics, not military experience, that decided who was to get the hetman's office.