The Slovak military participated in the war on the Eastern Front against the Soviet Union. The Slovak Expeditionary Army Group of about 45,000 entered the Soviet Union shortly after the German attack. This army lacked logistic and transportation support, so a much smaller unit, the Slovak Mobile Command (Pilfousek Brigade), was formed from units selected from this force; the rest of the Slovak army was relegated to rear-area security duty. The Slovak Mobile Command was attached to the German 17th Army (as was the Hungarian Carpathian Group also) and shortly thereafter given over to direct German command, the Slovaks lacking the command infrastructure to exercise effective operational control. This unit fought with the 17th Army through July 1941, including at the Battle of Uman.