Do you want to stop your neighbors' expansion in their tracks, but you can't afford a war with them right now? The answer is simple: research Animal Husbandry as soon as possible, then start working on getting Hunting. Why Animal Husbandry, you ask? Two words: giant spiders. Once you've unlocked the Subdue Animal promotion, those annoying, invisible killers of units will become the best thing since sliced bread for you. Every hunter you have will be out scouring the wilderness for more spiders, capturing them, and bringing them home to turn into economic-warfare units. Scouts tend to die to spider attacks, but hunters, with their base strength of 4, tend to survive them. So as soon as you've researched Hunting, start building a few hunters and sending them out into the wilderness. Get then up to 5 XP by fighting barbarians as often as possible (try to wait on killing animals, as every animal you kill is one animal you can't capture later on) and then give them Combat I and Subdue Animal. Now you're ready to go spider hunting. The great thing about giant spiders, you see, is that they start with Hidden Nationality. This allows them to enter your neighbors' territory even when you're not at war with them, and to attack your neighbors' units without declaring war. Now, animals get a -25% to city attack, so spiders will be all but useless at attacking city defenders (unless your neighbor is still defending with warriors only, and even then it's risky). No, the proper use of giant spiders is killing workers. The AI never seems to escort workers inside its own territory. So as your invisible spider roams around, you'll often find workers (or as I like to call them, "spider snacks") totally unguarded. Feed them to your spider, and keep exploring. Pretty soon you'll have mapped out your neighbor's entire territory, which helps prepare for invading them later on, and they'll have no more workers. Now it's time to settle your spider down on a hill with a good view of at least one of your neighbor's cities -- or even two cities at once if you can find a good spot. The AI hates having no workers at all, so it will probably shift at least one of its cities to producing workers. Which means that city won't be growing during that time, and won't be producing military units or buildings either. Once the worker emerges from the city and heads off to work on improving a tile, simply march your spider over there and eat the worker, forcing the AI to start producing yet another worker. What's more, every time you eat a worker, there's a chance your giant spider will produce a baby spider. If that happens, start using the baby spider to eat workers -- every worker it eats gives it a 20% chance of growing to be an adult. This trick would never work against human opponents, as they would quickly start escorting their workers with recon units to spot your spiders and deal with them -- but the AI will keep on sending unescorted workers over to the same spot where its last worker was munched on by an invisible spider. For just the hammer investment of building a few hunters, you can totally paralyze the economy of one of your neighbors, or even several of your neighbors if you captured enough spiders. This allows you to get to prime city spots before they do, keep them tech-poor so you can invade later, all sorts of things. It's a very powerful strategy.