[I am fully aware of the Chinese history. A lot of countries has similar things in their past and don’t qualify as global empires. China was always incapable to convert its economic power into a military power and they weren’t good at diplomacy. That disqualify them as an Empire.
As for Russia her expansion was only natural. There is no need in this anymore since the concept of defensive perimeter is mostly dated.]
What makes you think so? Really?