I especially enjoy the idea that newly acquired or created cities in the latter half of the game can receive help and supply in the form of developing pop growth and increasing hammers available. Reinforcing the economies of cities founded/taken at a considerable distance from the capital in the early game could be pivotal in securing choke points, resources etc. Settling in barren land becomes entirely possible with the assistance of domestic trade routes. I like the idea of transferring unit production to cities near the front but didn't think it feasible considering the lack of hammers (and pop if you razed it and cancelled the razing process before completely burning down the city) those frontier cities are left with after siege. This way an empire entirely engulfed by war can continue expanding by force at the expense of burning bridges that would have brought income by way of int'l trade routes. At the moment I am playing a huge emperor archipelago Mongol standard game (12 a.i. and max CS) and I am at the half way point of the game. My horde of Keshiks and Cavalry is unsustainable without war, remaining intact and not disbanded by looting cities and enemy units...my scouts i've filled cities for happiness bonuses have, turn-by-turn disbanded due to an economy of minus 60+ GPT. The only way to finish this particular Mongol game meaningfully is to dominate, but without domestic trade routes (I call those 'supply lines'), the war industry will remain considerably slow and reinforcements have ten turns worth of travel from homeland to battlefront; unacceptable. --- Establishing trade routes, in general, requiring protection will witness a burgeoning defense structure. Sea lanes must be secured, for instance, and a proper navy must be developed to enforce. On another subject archaeological digs in and through foreign lands would demand basic diplomacy (embassy and borders) with said civ or else ignore culture or take over those borders which digs lay behind. A warring nation from the get go may find resistance in gaining access to digs in hostile lands, but prior battles should provide the supply of digs available later in place of making the trip into opposing lands.