Original sentence: The British Navy, generally supportive of Satsuma and Chōshū, was maintaining a strong fleet in Osaka harbour, a factor of uncertainty which forced the Shogunate to maintain a significant part of its forces to garrison Osaka rather than commit to the offensive towards Kyōto
Edited sentence: The British Navy, generally supportive of Satsuma and Chōshū, was maintaining a strong fleet in Osaka harbour, a factor of uncertainty which forced the Shogunate to maintain a significant part of its forces to garrison Osaka rather than commit it to the offensive towards Kyōto.This foreign presence was related to the very recent opening of the ports of Hyōgo (modern Kobe) and Osaka to foreign trade since 1 January 1868