Aye! Thank you very much - this is all extremely helpful! From suffering a defeat every time I fought the Almohads at even odds, I have just won 3 battles in a row with the odds against me at 3:1 - in Morocco!
When I attacked the HRE through Provence, Savoy, Burgundy and Schweiz, taking a foothold in central Europe, I had no difficulty in despatching 1300 spears, swords, archers and knights upon a mountain with the aid of 1 archer group, 4 swords, and 5 medium cavalry.

I now own Iberia, Morocco, and the mentioned German provinces. I am at war with the re-emerged Almoravids in Algeria - and excommunicated because I disallowed a German crusade from creating desertion in my three central European armies. Up until 1172 I was receiving 1000 florins from the pope every third turn - I had never attacked a Catholic without his sanction - and I had engaged in two successful crusades.

France has just declared against the small HRE. The French are my allies, but they are distrusting. I have 3800 men on south of the Pyrenees, France has 4300 in the north.
Due to their 70 year uninterrupted peace, they have many technological advantages over me - mainly in armour.

I am unsure if I should attack now with a newly furnished army in Brittany, and thus trap all of France between my other armies in; Burgundy, Provence, Aragon, Switzerland, and Navarre. Each consists of generally 3 F.S., 4FMAA, 2 Archers, 3 Andalucian Cavalry, 2 Royal knights. Generals range between 4 and 8 stars. 3 armies are veteran quality.

My main dissuading factors are my fear for influence, (I have just been excommunicated, and France is my ally, and has been since 1129. Also, she is allied to all but 3 of my other allies - and very intimate with Genoa, a small kingdom with a military of 2100 threating Provence.), defeat at the hands of superior armour, and a constant worry that another war will place me behind the East in the coming shift to Chivalry.

Should I invade Brittany, or strengthen my borders and continue building in Iberia?