At the same time, due to the efforts of Wasilewska and Zygmunt Berling, a new army was established—the Polish People's Army ("Ludowe Wojsko Polskie", LWP). Its first unit, the Polish 1st Tadeusz Kościuszko Infantry Division ("1 Dywizja Piechoty im. Tadeusza Kościuszki"), was created in summer 1943, reaching operational readiness by June/July. In August, the division was enlarged to a corps, becoming the Polish 1st Corps. It was placed under command of General Berling; other notable commanders included General Karol Świerczewski and Col. Włodzimierz Sokorski. The division with its supporting elements was sent to the Eastern Front in September 1943 and its first major engagement was the Battle of Lenino. By March 1944, the corps had been strengthened with increasing armoured and mechanical support, and numbered over 30,000 soldiers. In mid-March 1944, the corps was reorganized into the First Polish Army.