The mongols invaded china with the intentions of having china under the Mongol Yuan rule.
The destruction of our power grid.
The romans used all of these things because they wanted to build a huge empire. Unlike the Greeks who did that stuff for fun the Romans want to use those skills as a way to be at the top
Hope this helps
The local lords pledged their loyality to Shogun during the Japanese ideal system.
Spain's motives for colonization were threefold: to locate mineral wealth, convert the Indians to Christianity, and counter French and English efforts. The Spanish colonization system was highly successful