On 21 February 1831 Umiński rejoined the Polish Army. Initially in the rank of an ordinary soldier, Umiński took part in the First Battle of Wawer and the bloody Battle of Olszynka Grochowska. Soon he was discovered by his former colleague, General Henryk Dembiński, who promoted him to a Colonel, then a Division General, and gave him command over the I Cavalry Corps. His Corps took part in the battles of Jędrzejów and the Battle of Ostrołęka, one of the bloodiest battles of the uprising, plagued by indecisiveness and bad command decisions on the side of the Polish Commander-in-Chief General Jan Zygmunt Skrzynecki. Critical of his superiors, Umiński nevertheless remained in the army until the very end of the uprising, taking part in the lengthy battle of Warsaw. Following the Polish defeat, he led the remaining Polish forces to Modlin and Płock, where on 23 September 1831 he was nominated to the post of the Polish Commander-in-Chief. Opposed by many generals, he held it for only a single day and ceded his duties to General Maciej Rybiński.