 Complete the following phrase:  Under Ottoman rule, Nikopol developed into an important military and administrative centre as a sanjak, with a strong fortress and a flourishing economic, spiritual and political life, until it went into decline during the 17th and 18th centuries. It was the centre of a district kaza, but it was overtaken by Pleven as the regional centre of that part of the Bulgarian lands. Nikopol was captured by the Russians in the 