by hokuto_su
I agree with Brian on that you might need to fight a culture engine with military in an attempt to force their hand. But I have some doubt myself whether or not it is the best way, for, heavy military (the type that prepares you for a war) costs a lot and requires quite a bit of luck.In order to scare your opponent into building military, you need a high strength (probably more than a defense card's worth than your opponent), which mainly comes from units and tactics. Thus, it translates to
1. a steady supply of food and resources to build your military force
2. availability of more than 1 military technology cards and compatible tactics
3. more than 1 war or aggression cards
4. from points 1,2,3, it means you need lots of military actions such that you can build military units, draw & play tactics and aggression. This means you need a government or military special tech upgrade
5. from points 2 and 4, it means you need at least 10+ science points (warfare, knights and swordsmen cost 11) in addition to whatever science points that you use to upgrade your farm, mine and labs
That's a hell lot of investment and you still are not guaranteed to get the tactics and aggression cards you want!