What the?????

[Rilder]

bring all my reinforcements at once in my first try

Open RTW folder(or EB if you renamed the folder)\EB\Preferences\preferences.txt

scroll down to "UNLIMITED_MEN_ON_BATTLEFIELD:FALSE"

Change the false to true.

Edit: actually might be the preferences in the rtw\prefrences\prefences.txt now that I look at it.