I think the orders came from Gardener. Yes I agreed. It must have been the first thought to get the hell out of it. Dalton was an old sgt of the line and had Battle exprience. It does seem that Chard wasn't included in the decision to stay. As you say fortifications were already on the way when Chard came up from the river. But his engineering knowledge did came in handy when constructing the redout, which of course was there last safe haven.