On several instances, I have seen the argument made that during the Red River Campaign, Banks made a fatal error in not following the river road from Natchitoches to Shreveport, as by taking the inland route, he denied the Navy the ability "to provide support for the infantry."

Is this a legitimate argument? While naval gunfire of the time could certainly throw a projectile several miles, with the low stage of the river and the lack of indirect-fire capability of the naval guns (no radios, therefore no ability to use forward observers), could gunboats actually have provided any kind of support to the infantry? Supplies maybe, but that would be better provided by packet boats (protected, of course, by the gunboats). It seems I've seen this argument made before, and it has always seemed anachronistic to me. I came across it again today. Am I missing something?