Complex sentence: From 1914 to until 1919 it's primary tasks was to seek out and destroy German commerce raiding forces, during the interwar period it resumed the work of maintaining and refitting vessels stationed here and those travelling en-route to Asia.
Split into simpler sentences: From 1914 to until 1919 its primary tasks was to seek out and destroy German commerce raiding forces. During the interwar period it resumed the work of maintaining and refitting vessels stationed there and those travelling en-route to Asia.