You should have both. You researched Horseback Riding in year 12, and Animal Taming in year 10.
Excellent! How fortuitous.
The defense still seems a little weird...
My Lactosian Infantry with iron shields have 5 defense. My Heavy Scouts with strong iron shields and tower shields have 8. So, it seems likely that strong iron gives +1 defense over iron, and that tower shields give +2 defense over normal shields, or strong iron gives +2 and tower shields give +1. Also, steel shields are presumably stronger than strong iron shields. Thus, my Heavy Hand Cannoneers should have at least 7 defense, I think... there are several explanations for this.
1. Steel shields are not stronger than strong iron shields in terms of pure defense (in this case tower shields give +2 to defense and strong iron gives +1).
2. Strong iron shields are not stronger than iron shields in terms of pure defense (in this case tower shields would give +3).
3. Strong iron shields give +0.5 defense, tower shields give +2.5 defense, and steel gives +0.5 defense over strong iron.
4. Cannoneer units have reduced effectiveness on shields (again, I'm not sure what the "won't be penalties" thing means specifically).
5. Defense is calculated holistically, not through pure buffs and debuffs alone, and by some other mechanism my cannoneers have been assigned 6 defense.
Knight, can you confirm which, if any, of these situations is correct, or is that against the rules/spirit of the game?