In the beginning of September 1813, the Serbian rebels were defeated at Ravnje, by a strong Ottoman force commanded by French officers. The rebels were forced to retreat; Čupić swam over the Zasavica and arrived at Šabac, where he together with his blood brother, "vojvoda" Luka Lazarević, started organizing the defence of the city. When the Ottomans assembled a very large force outside the city, the rebel soldiers run asunder, leaving the commanders, who concluded that it was impossible to defend the city. Luka Lazarević sent his family to Syrmia, while he, Čupić, and their men descended the Sava to Zabrežje, from where they crossed the Sava into Austrian territory (Military Frontier), in order to save their lives. As other commanders, he found refuge in Syrmia. However, after a short period of time, he returned to Mačva, staying in the forests.