Reviewing AI tech progress here is an idea of the best enemy units we can expect to face in conflict with the various nations.
Caesar: SAM infantry, machineguns, knights, artillery, frigates, ironclads, and airships.
Monty: muskets, cuirassiers, trebuchet, galleons.
Justinian: muskets, machineguns, knights, cannons, destroyers.
Tokugawa: mace, knight, trebuchet, galleon.
Churchill: rifle, machinegun, cavalry, artillery, frigate, ironclad, airship.
Gandhi: rifle, machinegun, knight, artillery, frigate, ironclad, airship.
Oil and uranium sources are critical to the development of modern military forces. Gandhi has a uranium source under one of his cities, so we can’t stop him from developing a modern fleet, but spy missions could potentially deprive him oil access. Spy missions could pillage both Churchill’s oil and uranium tiles halting all modern unit production there. The same goes for Justinian’s single oil resource.
Justinian is currently at war with Gandhi and Churchill is at war with Tokugawa. Considering the technological disparity between these foes it is a wonder that so little progress is being made. The wars are over seas invasions though so will likely have little long term impact unless a weakened Tokugawa can entice Gandhi to conquer his entire continent. Likewise Churchill may decide to join with Gandhi to conquer Justinian. Current AI relations indicate that this is not likely.
If we are going to attempt a conquest or domination win an attack on Tokugawa would deliver quick results as well as 5 more resources for Mining Inc.