Complex sentence: He worked on strengthening the Ottoman rule over Syria, Egypt, and Iraq; however slight successes against rebellious outbreaks in Syria and the Morea could not compensate for the loss of the Crimea which Russia greatly coveted.
Split into simpler sentences: He worked on strengthening Ottoman rule over Syria, Egypt, and Iraq. However, slight successes against rebellions in Syria and the Morea could not compensate for the loss of the Crimean Peninsula, which Russia greatly coveted.