Stage 1 - Yellow Turban Rebellion

Objective Changes & Effect
Rescue the peasants. Enables Zhang Jiao to appear in later battles.

The area in the center of the map will have peasants calling for help, there are three spots they can spawn at. Just simply defeat the troops around them before you defeat Zhang Jiao.

Stage 3 - Defense of Xu Province

Objective Changes & Effect
Defeat the retreating enemies. Effects the Battle of Fan Castle.
Do not defeat the retreating enemies. Unlocks Disturbance at Guandu.

For this objective it is best to play as Zhang Fei due to his missions leading him to the boulder devices. When the units appear make your way to where their exit point is at in the West. Wait for them to come to you and defeat all of them before they leave after Guo Jia gives the order for them to retreat.

Stage 6 - Battle of Chibi

Objective Changes & Effect
Find Xu Shu after the fire attack succeeds. Enables Xu Shu to appear in later battles.

After the fire attack works Xu Shu will be located in the North ship areas, you can see his location in the unit info. He has no lifebar so you can't hurt him.

Stage 7 - Battle of Chengdu

Objective Changes & Effect
Ensure Pang Tong's survival by uncovering Zhang Ren's ambush. Enables Pang Tong to appear in later battles.

In the base Qiao Zhou is at you will notice a black square on the right side of it, though not shown on the map this is where Zhang Ren will be at waiting to ambush Pang Tong with archers. Defeat him before Pang Tong moves to where they would ambush him. If playing as Pang Tong go there and defeat Zhang Ren before making your way around the back.

Stage 8 - Battle of Mt. Dingjun

Objective Changes & Effect
Defeat Cao Xiu. Affects Battle of Fan Castle.

Very simple objective.

Stage 9 - Battle of Fan Castle

Objective Changes & Effect
Complete all star objective of previous stages. Enables Xu Shu to appear unlocking the Hypothetical route.

Have all objectives complete when you reach this point in the story and talk to Xu Shu for the Hypothetical route.

Historical Stage 12 - Battle of Jieting

Objective Changes & Effect
Rescue Ma Su before he gets trapped. Unlocks Battle of Chencang.

To rescue Ma Su you have to save Liao Hua, Gao Xiang, and Xiang Lang before activating Cao Hongs ambush.

Historical Stage 12X - Battle of Chencang

Objective Changes & Effect
Ensure Zhang Bao's survival by uncovering the ambush. Prevents Zhang Baos death scene from occurring.

For this you have to play as Zhang Bao otherwise the AI will run straight into the ambush. Complete all objectives normally until you get to storm the castle, do not go straight forward into the small room with 4 doors as it will kill Zhang Bao after the battle ends. Get a catapult and drive it to the path West of the doors to see a crack in the wall, fire to open it and enter one of the two empty areas to uncover the ambush units.

Historical Stage 13 - Battle of Wuzhang Plains

Objective Changes & Effect
Eliminate the enemy messengers. Extends the after battle cutscene.

It is recommended that you play as Wei Yan or Ma Dai for this objective. You will need to be fast to be able to defeat both messengers when the order to retreat is given don't retreat and wait for a messenger to appear then immediately go to the other side, as Wei Yan or Ma Dai you will have an easier time as there's a ledge you can jump down from which skips a large portion you would have to walk around if you were Jiang Wei or Xingcai.

Hypothetical Stage 10 - Battle of Lukou

Objective Changes & Effect
Successfully foil all of the enemy plans. Enables Lu Xun and Lu Meng to appear as reinforcements in Ambush at Chang'an.

Follow all of Zhuge Liangs orders to successfully foil all of Wus plans, for Lu Mengs plan circle around back to ambush him as he feigns to lure your forces. If Lu Meng sets up ballistae then you will have failed the objective.

Hypothetical Stage 11 - Ambush at Chang'an

Objective Changes & Effect
Defeat Xiahou Mao before Guo Jia appears. Unlocks Pacification of Nanzhong.

Follow the flow of the battle, when the makeshift bridge is released make sure to follow it and then rush to Xiahou Mao after it completes the path.

Hypothetical Stage 11X - Pacification of Nanzhong

Objective Changes & Effect
Defeat Zhurong three times. Enables Meng Huo and Zhurong to appear as reinforcements in Invasion of Luoyang.

A simple objective like Meng Huo there are two points outside of the main camp where she will appear simply defeat her in those two points before her final one at the main camp.