In spring of 1809 Poniatowski led his army against an Austrian invasion under the Archduke Ferdinand Karl Joseph of Austria-Este, in the war that was regarded by Austrian high command as a crucial element of their struggle with Napoleonic France. At the bloody Battle of Raszyn near Warsaw on 19 April, where he personally led his men in an infantry bayonet charge (throughout his career he did a number of these), Polish forces under Poniatowski's command fought to a standstill an Austrian force twice their number. Afterwards however decided not to defend Warsaw and withdrew with his units to the east bank of the Vistula River, to the fortified Praga suburb, which the Austrians attacked, but were defeated at Grochowo on 26 April. An Austrian division then crossed the Vistula again trying to pursue the Poles, but was routed on 2 May at Góra Kalwaria in a daring attack led by General Michał Sokolnicki. Ferdinand made a couple of attempts more, trying to establish a bridgehead on the other side of the Vistula, but those were defeated, which left the initiative in Poniatowski's hands. From there he quickly advanced south, staying close to the Vistula to control the situation and taking over large areas of Galicia, that is southern Poland that was controlled by Austria under the partitioning arrangement. On 14 May Lublin was taken, on the 18th fortified and vigorously defended Sandomierz. On the 20th the Zamość fortress was overpowered, where 2000 prisoners and 40 cannons were taken, and even further east Lwów was taken on 27 May. These military developments compelled the Austrians to withdraw from Warsaw — a counteroffensive by their main force resulted in the retaking of Sandomierz on 18 June.