Complex sentence: He was company commander in 16th Zemgale Police battalion, which was involved in anti-partisan duties in the Leningrad Front (near the Lake Ilmen and Staraya Russa).
Split into simpler sentences: He was company commander in 16th Zemgale Police battalion. Battalion was involved in anti-partisan duties in the Leningrad Front (near the Lake Ilmen and Staraya Russa).