Following the Battle Hostile_encounter of Raszyn on April 19 , the Polish forces commanded Control by Prince Józef Poniatowski left Warsaw undefended and withdrew Escaping to several fortresses located nearby ( most notably to Modlin Fortress and Serock ) .

Overnight of April 24 the Polish force left Departing Serock and crossed Motion_directional the Narew , reaching Arriving Radzymin before daylight .