blitzkrieg1980
Octobrist
CR3 trebs crunch grens. CR3 cannons (you can get steel without economics) crunch everything. Also, you can upgrade CR3 trebs to cannons. I like to do both. If you need to upgrade them to arty, you didn't build enough in the first place.
CR3 = -75% (total) to opponent base str. A gren becomes a 3. A rifle becomes a 3.5. They are not even the equivalent of longbows against CR3. An infantry becomes a 5.
You can see how 8s and 12s crunch them. You can use archers to get the kills.
IF you are spain and finish engineering, the only thing you should build for a few hundred years are cits and trebs and cannons.
As a quickspeed 3-city conquest player (MP except for strat generation), I find little use for + trade routes.
Unfortunately, the 75% does not come out of base strength, rather it is subtracted from the bonuses the defender has and whatever is left applies to the base strength.
Based on this fact, you've forgotten the 25% bonus that all these defenders have for fortification. Plus, if the city is on a hill (which many AI cities are) that's another 25%. Also, for even an AI to have no upgrades by the time grenadiers are around is almost impossible. Let's take in the most likely situation.
Grenadier (12) + 25% Fortify + 25% On hill + 45%(City defender I & II) - 75% for city raider I/II/III is Grenadier (12) + 20% still left from bonuses = 14.4 vs. a cannon 12.
even worse for Rifleman, and nearly impossible for infantry (16.8 and 24 respectively & after bonuses)
Artillery with CRIII will trump most, but still fall to it's knees at the hands of a city defender marine (as marines receive a +50% bonus vs. artillery)