THE PROBLEM

Every time you start a campaign with any faction there's a small introduction on how is recommend to start your expansion regarding the faction your playing, and this will only happen ONCE, even if you immediately exit to the main menu and start again with the same faction it will not play the same introduction and simply skip it.
This happens because there's a code on the "campaign_script.txt" that monitors your campaign starts so that it will skip the introduction on the next start, it was design so that it's does not delay your "Impetus" to start a game, before the time of youtube let's play and such were popular.
It kinda blows if you need to restart recording if something went wrong and you won't be showing the intro, I think.

And the only answer that you would be seeing, when searching with your friendly search engine regarding that is, to Reset the Advisor.

The Interwebs Solution

As mention before the solution to fix the problem on the webs is to Reset the Advisor, and how you do that?
You start a game/load head to Game Options and tick the Reset Advisor Box, save it, return to the main menu and start a Campaign, again, and by doing that NORMALLY or SUPPOSEDLY it should work but it does not, even if you set the Advisor Options on the bottom left corner in the campaign start screen to TELL ME EVERYTHING, it will still not play the introduction moves animation.
I, myself, try it and did not work as well this solution can trigger the monitor code in the campaign script, making it useless.

As such I found two possible solutions.

They are 2 possible solutions to fix this, test them myself.


This Solution as worked out for me before, and it's safe, compare to the other one, but it takes more time, you just need to delete local content from the steam library by right clicking on the game or run the uninstall on the game folder if you still own the cd/dvd of the game, and then reinsalled with them or download it again from steam.
NOTE: That even with save files I cannot guarantee that with will fix it, since for me I delete it everything.

And if you/I want to play with a locked faction? Do I have to complete a campaign with the starting factions to play with the faction I/you want?

If you want yes, if not you can try and do the following on this wiki on the Total War Center link:
http://www.twcenter.net/wiki/HowTo:Unlock_All_Factions#Medieval_2_Total_War

Although I'm not aware that this will trigger the monitor code, can't say for sure, since I can't remember.


This Solution can be unsettling, since it involves changing the campaign script which includes the game code itself, but it works, since I try it myself recently.

Here's how you do it:

Go to your game folder:
Left click on the icon, properties, open install folder, if you installed with the cd/dvd
or
On your steam library, properties, open install folder

it should be something like this regarding the case:

Steam\steamapps\common\Medieval II Total War

Programs\SEGA\Creative Assemble\Medieval II <- not sure if it's corrected

Next, head to the folder where the script is, the imperial_campaign folder

"Medieval II Total War\data\world\ maps\ campaign\imperial_campaign"

and you should see the "campaign_script.txt", normally is the first file, and open it with notepad, notepad++, or any text editor program.

JUST IN CASE create a backup file, by copying it and paste it or on the same folder or on the desktop.

After opening it search for the faction that you are interest in playing has, and you will something has below.
NOTE: The Byzantines are labeled has Byzantium.


And you can see the monitor code for the faction(s) introduction moves underlined.
To enable it again, the introduction moves animation, you simply need to delete the last two lines on the first paragraph has you can see it below:


NOTE: You need the same lines for everytime you want to play with a faction, if not playing the introduction moves, since this is not universal and it's faction specific.

As you can see it's quicker than the first one, if you follow it correctly it should not give any problems.

Hopefully this as help you as it has help me.
Also, since I'm not a english native speaker, I apologize for any butchering.
If you have any questions posted down below in the comments and a thanks is always appreciated. :)