I don't know that I have seen anything that was an official consolidation. I have searched and foundnothing. It may have been that they retained their identity by keeping their own company designations but acting as two wings of the regiment....Col commands regiment, commanders of 1st and the 15th commanded their wing (regiment), Unlike the 11th and 17th Infantry where the companies of the 11th were consolidated into A-G and 17th made up H-K of the new regiment.