Complex sentence: When hostilities began, the Chinese advanced a guarantee of safe passage in exchange for his retreat to south of Liaoyang, it was declined, and instead Mishchenko called for more Russian troops to reinforce his position.
Split into simpler sentences: When hostilities began, the Chinese authorities advanced a guarantee of safe passage in exchange for his retreat to the south of Liaoyang. This was declined, and instead Mishchenko called for more Russian troops to reinforce his position.