Complex sentence: With this new knowledge in combination with other measures of diplomatic modernization, China managed to maintain peaceful relations with the foreign powers throughout the 1860s, this provided her with a suitable environment with which to pursue domestic reforms.
Split into simpler sentences: With this new knowledge in combination with other measures of diplomatic modernization, China managed to maintain peaceful relations with the foreign powers throughout the 1860s. This provided her with a suitable environment in which to pursue domestic reforms.