Playing through the historical stages on story mode and then both unlocking and playing through the theoretical stages will get you the majority of these events. More so if you manage to complete all of the in-map objectives (E.g “destroy the arbalests!”, “Quickly get to Liu Bei!” etc.) However there are a few that won’t unlock this way, or at least didn’t for me and so I spent some time researching, and testing out and have brought all of the information I found here, into a guide on how to get some of the more obscure events.
Wei:
#24 “Father and children” (beneath ‘Strength Combined’ and above ‘A Warrior’s resolve’)
On the Battle of Mt.Dingjun, wei story line, simply follow the stage as standard until Huang Zhong appears and heads to the north west of the map. All you have to do is sit back and let him kill the officer there (Xiahou De, I think), before he charges into the main camp. He will say a few lines and so will Xiahou Yuan and at this point he will probably get mobbed by Zhang He and a few others and subsequently flee, so just finish the level as normal after this to obtain the event.
Wu:
#15 “Fleeing Towards Hope” (beneath ‘Ambition Passed Down’ and above ‘Interupting the Raid’)
Battle of Hefei. (This one may look like complicated, but it is actually quite simple- I’m just adding a lot of detail to try and be as helpful as possible.) Play as Sun Quan here, and select Taishi Ci once in camp to begin the historical playthrough. At the start, just ignore everything and stay still (Lu Su will start chatting if you’ve saved him en route to unlocking the hypothetical stages) Zhang Liao will appear, destroy a bridge and then run off. Head north with your troops towards the castle and, after you’re across, the bridge will raise, stranding you. Follow Sun Quan’s directions and follow the west path back to the base, killing everyone until you re-unite with Taishi Ci. At some point Sun Quan will order the retreat and a small escape point will appear, you must not go straight here if you want the scene to unlock. Instead, continue south from Taishi Ci’s base once the door opens and start to rescue your allies. As you near the second base along, Zhang Liao will attack and a scene will occur with him and Taishi Ci. Afterwards, defeat him and move to the main camp (A bit east, then north. If you can’t remember where it is Xia Ku is there at the minute). As you enter, Li Dian will trap you, so beat his ass, enter the base and kill Xia Xu. Afterwards, head to the east side of the base and ride up the stairs there, jumping over the Ledge with the green arrow to find yourself at the bridge that Zhang Liao destroyed at the beginning. You will be prompted to jump over it by a big yellow circle, so do so and (Finally) obtain the event. After which, it is a simple matter of beating down Zhang Liao to finish the stage.
Shu:
#3 “A Journey Without Light” (Beneath ‘An Illuminated Path’ and above ‘Rise of Tyranny’)
The Yellow Turban Rebellion. I played as Liu Bei, though I’m not sure it matters. Play through the level until you split your forces east and west. Sometime shortly after, Peasants will appear in the big central village, begging to be saved. Guo Si will suggest, kindly, that you don’t save them. In order to obtain the scene, you must not save these peasants at all, so just ignore them and continue on to the end of the stage and defeat Zhang Jiao to obtain the event.
#13 “The Prodigy’s Plan" (Beneath ‘The Face of Benevolence’ and above ‘The Children of the God of War’)
Battle of Mt.Dingjun, Shu. You must have saved Pang Tong at the Battle of Chengdu prior to this (If someone would like me to elaborate on how to do that then please let me know and I will add it to the bottom of this). A lot of people online are after this event, and the only response is the battle of Chengdu, but actually you only need to have done that to allow Pang Tong to appear here, and so the event triggers. Just play the level as normal: begin, take the bases and proceed up the western path killing as you go. It may not seem like much has changed, but as you finish the stage Pang Tong will appear, right at the end of the event, and say a couple of lines.
Jin:
#7 "Narrow Ideals" (Beneath 'The Man of Virtue's Path' and above 'A Bloodline Curse')
East Gates Battle. Play as Sima Zhao. This one requires a little standing around, in order to help your allies die, and i would definitely play on normal difficulty or above for the same puprose. From the starting point, remain standing without killing until either one of your officers dies (for me it was Hu Zan) or until the wu forces begin to retreat, this is to try to keep the morale bar low, again helping your own side to die. Personally, after Hu Zan died, I raced in and killed the three officers in the western base, triggering the retreat. Follow the remaining two green-boxed officers south, without killing them, and branch off east when Sima Zhao starts moaning about the plan. Zhuge Dan will go south with his forces and become ambushed there, as will Sima Zhao (You) to the east. Quickly kill the ambush officer near yourself and then wait in the area where they spawned. If you kept the morale bar low (I hadnt killed more than 100 men at this point) then one of the officers with Zhuge Dan should die. When one of them does, you will get a report from a messenger and Sima Zhao will task you with saving Zhuge Dan then retreating. As far as I can tell, that is the conditions for this event met- all you have to do now is finish the map by killing the officers on the way to Zhuge Dan. As you get near him, the ally officers with him should start dropping like flies, but Zhuge Dan himself should be fine. He will charge to a central garrison as you near him too, leaving some enemy officers behind in the base where he was ambushed. Not sure if this is essential, but after meeting up with him I killed all of his pursuers, but left those officers alive who were not chasing him. Once you have met up with Zhuge Dan, follow him to the north, killing all wu reinforcements when they appear and, at the escape point, you should be met with the event.
I did all of these in story mode so I would recommend the same as I'm not sure if it works in free mode tbh. Still. Hope this helps and if anyone needs any other ones then let me know and I’ll see if I can work it out and update the post. Oh and let me know if you have any problems with my wording and I’ll try to make it a bit clearer.
I also don’t take credit for finding these out, merely bringing the answers into all one place, as all of the information required for me to write the above was found around Gamefaqs, IGN, and a few other sites.
Good luck.
UPDATE: Cheers to both Psxfreak101 and OzzieDeath for their help with Shu #13, updated it without the need to worry about Cao Xiu.