Complex sentence: The small maintenance garrisons in the Verdun forts had to report to the central military bureaucracy in Paris and when the XXX Corps commander General Chrétien, attempted to inspect Fort Douaumont in January 1916 he was refused entry.
Split into simpler sentences: The small maintenance garrisons in the Verdun forts had to report to the central military bureaucracy in Paris. When the general in command of the Verdun sector atempted to inspect Fort Douaumont in January 1916, he was refused entry.