Complex sentence: It was placed under Russian administration between 1828 and the Crimean War, with an interlude during the Bucharest-centred 1848 Wallachian revolution, and an Austrian garrison took possession after the Russian departure (remaining in the city until March 1857).
Split into simpler sentences: It was placed under Russian administration between 1828 and the Crimean War, with an interlude during the Bucharest-centred 1848 Wallachian revolution. Later on an Austrian garrison took possession after the Russian departure (remaining in the city until March 1857).