A basic answer would be that if they had been capable of such an advance, they would have made it. The day's battle left them very disorganized and worn out. The Union retreat had pulled the Union troops back into a strong defensive position in the Alexandria area, supported by forts. The South simply didn't have the numbers to force the issue at this point. Having said this, I have not really made a detailed study of this battle and I'm sure there are more capable people who can answer this in detail. -- Al