"Plutonowy" is not a platoon leader. It is a military rang but not a function. In the English it is a staff sergeant ( Air Force) or master corporal ( Army).
In the case, Master Corporal Józef Jabłecki was servicing in the 5th Anti-Aircraft Artillery Regiment. The unit belonged to the 5th Kresowa Infantry Division that was fighting as the part of the 2nd Polish Corps in Italy eg.. at the Monte Cassino, Ancona, the battle on the Gothic Line and in the Battle of Bologna staying untill the end of the war in the Italy. In September 1946 the regiment together with units of the II Corps was moved to the Great Britain.