Mikołaj Potocki and Marcin Kalinowski, he began moving on his own, soon learning about the second Cossack victory at Battle of Korsuń, which meant that his troops (about 6,000 strong) were the only Polish forces in Transdnieper at that moment. After taking in the situation, he began retreating towards Chernihiv; his army soon became a focal point for various refugees. Passing Chernihiv, he continued through Liubech to Brahin. He continued to Mazyr, Zhytomir, and Pohrebyshche, stopping briefly in Zhytomir for the local sejmik. After some skirmishes near Nemyriv, Machnówka and Starokostiantyniv (Battle of Starokostiantyniv) against the Cossack forces, by July he would arrive near Zbarazh. Wiśniowiecki's fighting retreat had a major impact on the course of the war. In the words of the historian Władysław Konopczyński, "he was not defeated, not victorious, and thus he made the peace more difficult." Politicians in safe Warsaw tried to negotiate with the Cossacks, who in turn used Wisniowiecki's actions as an excuse to delay any serious negotiations. Around late August or early September, Wiśniowiecki met with the army regimentarzs Władysław Dominik Zasławski-Ostrogski, Mikołaj Ostroróg and Aleksander Koniecpolski. He was not on overly friendly terms with them, as he resented being passed in military nominations, but after short negotiations, he agreed to follow their orders, and thus reduced to a junior commander status which had little impact over the next phase of the campaign. On 23 September, their forces were, however, defeated at the Battle of Pyliavtsi; near the end of the battle some accounts suggest Wiśniowiecki was offered the hetman's position, but refused. On 28 September in Lviv, Wiśniowiecki, with popular support, was given a field regimentarz nomination; about a week later this nomination was confirmed by the Sejm. To the anger of Lviv's townfolk, he decided to focus on retreating towards the key fortress in Zamość instead of Lviv; he would leave garrisons on both towns, and keep his army in the field. In the end, the cities were not captured by the Cossacks, who in the light of the coming winter decided to retreat, after being paid a ransom by both town councils; no other large field battle took place that year. Meanwhile, the convocation sejm of 1648 had elected a new king, Jan Kazimierz II Vasa. Wiśniowiecki supported other candidates, such as George I Rákóczi and Karol Ferdynand Vasa (Jan Kazimierz's brother). Due to the opposition from Jeremi's detractors, he