Algesan,

That is dependent on whether or not you have grouped your troops. If you have them in a formation you desire and then move them up without first grouping them, they will all advance at their individual speeds.

If on the other hand you have grouped the formation they will then all advance at the rate of the slowest unit in the group.

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Obake

I warned you, but did you listen? Ohh, no...it's just a harmless little bunny, isn't it?