God dammit Poland. I needed the winged hussars to arrive to defeat the Ottomans and they peaced out for no reason in the middle of the war >:C
Europa Universalis IV
Friggin' Ottomans.
Why do my armies keep getting their morale cut in half when I attack the Ottomans? I can have half again as many men as they do and still lose the battle.
Because the game hates you.
Ah, but seriously, some possibilities:
1. Generals. Good generals give significant bonuses. Shock and Fire are flat bonuses, but even Maneuver can play a role around rivers and straits (see below).
2. Military tech. If they outstrip you technologically (and if historical lucky nations are enabled, they have extra points to invest in tech), they may have superior "military tactics" points. This also plays into chosen units, as better units have more offensive or defensive pips, and multipliers, as better tech gives you better unit modifiers.
3. National advisors. Again, historical lucky nations get a bonus due to paying less for upkeep on advisors. +10% in straight morale from army reformers and +5% discipline (indirectly boosting inflicted casualties and morale damage) from commandants are the two to watch out for in combat itself; the others affect how many troops they can field or how quickly they can replenish losses.
4. Piety/Religion. As a Muslim nation, Piety can give them a 10% bonus on starting morale, while for anyone, picking up Defender of the Faith is another 5%. If they somehow went Shia, that's another 5%, but for the Ottomans, that's less likely.
5. Army Tradition/Power Projection. If they've been fighting a lot, 100 tradition will give them major bonuses (+25% morale, +10% morale recovery), and if they've been fighting rivals specifically, Power Projection is another +10% morale at 100 power.
6. Prestige. Another +10% to morale here at 100 prestige, but on the flip side, if your prestige is negative, your own morale can drop by as low as -10% at -100 prestige.
7. Terrain. If you're attacking, terrain works against you. Mountains are a flat -2 to the attacker's rolls; wooded/forested terrain, hills, and highlands are -1. If you don't have a leader with superior Maneuver, river crossings are a further -1 while straits and amphibious attacks are -2. If you attack from multiple provinces and even one attacker gets a penalty, all attackers gets the penalty.
8. (
EDIT) Traditions/Ideas. Ottomans always have +5% discipline, and their third national idea is +15% to cavalry combat ability. The rest depends on which ideas they pick. If they go Aristocratic, that's another +10% to Cavalry Combat ability. Defensive gives +15% to Morale. Offensive gives +1 to Shock and Fire pips and a further +5% to discipline. Quality is +10% to both Infantry, Cavalry, and Artillery Combat as they work their way up, plus 5% discipline at the top. In other words, there's a lot here.
Some of these, thankfully, work for you as well: prestige, army tradition, power projection, etc. Even the luck bonuses are thankfully more indirect than they once were, though I still tend to prefer either randomizing or deactivating them entirely. That's not an option if you're achievement-hunting, but otherwise, it might be worth considering.