 Complete the following phrase:  On , Tsar Nicholas I authorized Muravyov to carry the negotiations with the Chinese regarding establishing a border along the Amur River and to transport troops to the Amurs estuary. In 18541858, Muravyov assisted Gennady Nevelskoy in achieving that goal. The first expedition took place in May 1854. A fleet of 77 barges and rafts, led by the steamship Argun, sailed down to the Amurs estuary. Due to the Crimean War, a portion of the fleet was then sent to Kamchatkas Avacha Bay, where a series of artillery batteries was established to defend the peninsula. The batteries played a major role in defending the city of Petropavlovsk see 