There is a whole bunch of help files that comes with every game in the series. The most important is user.hlp that is also updated with every patch. Since it's rather brief, it's well worth reading entirely. From this file, regarding the issue at hand:
"Skirmisher Rule
In addition to the normal test, Routed Skirmisher units of non-Light, non-Guard units are only eligible to recover from Rout if they are within 5 hexes of their parent unit."
Also worth reading are notes.hlp, which explains some of the design choices and thus furthers the understanding for the way the the specific title was intended to work (whereas user.hlp is the same for all the titles) and npb.hlp, which is a description of all the menus etc. in the game (again, the same for all titles).
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D.S. "Green Horse" Walter, Maréchal d'Empire
Duc des Pyramides, Comte de Normandie
Commandant la [url="http://home.arcor.de/dierk_Walter/NWC/3_VI_AdR_Home.htm"]3e Division Bavaroise[/url], L'Armée du Rhin
Commandant [url="http://home.arcor.de/dierk_Walter/NWC/EdM_start.htm"]L'Ecole de Mars[/url], L'Armée du Rhin
Commandant la Brigade de Grenadiers de la Moyenne Garde

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