Complex sentence: The first period, coincidentally ended with the death of Alexander I and Decembrist Revolt in 1825, achieved surprisingly little success against "a handful of savages", as compared with the then recent defeat of Napoleon.
Split into simpler sentences: The first period coincidentally ended with the death of Alexander I and Decembrist Revolt in 1825. It achieved surprisingly little success against "a handful of savages", as compared with the then recent defeat of Napoleon.