Melee with large units

I'm a bit late to the party here, but if any experienced players are still around, can you answer this question?

If a large unit loses a melee, is it only the rear unit that retreats or is routed, allowing the front unit to carry on? This appears to be implied by the rules for firing against large units, and the particular rule that the entire large unit is removed after a flank or rear charge against it results in a rout.

Further, if a large unit does get split after losing a melee, can the 2 units re-unite at some stage?

Only just started with these rules. They are basically simple and I like the mechanics, but  to be honest I find they are often badly explained. I abandoned my first game in frustration after much head scratching, with the above point being the straw that broke this particular camel's back!

Hello Keith,
Large Units are like married people in a catholic marriage, united "until death do you part".

So the Large Unit retreats or pursues or takes any other action as a single Unit until the rear Unit (whoe takes the first losses in any circumstances) is destroyed.

Many thanks - it's good to know the support is still out there.