@Setanta,
Couch was seriously a competent leader, having led in The Peninsular CAmpaign, Second Manassas,Antietam,Fredericksburg and Chancellorsville. HE was promoted in each campaign for singualr leadership skills . HE resigned in disgust at Joe Hookers blunders in the latter. Couch was reassigned as commanadant of the Dept of the Susquehanna (, one of about 110 "Departments" theSusquehanna was a gateway to several key strategic war materiel production centers, like gunpowder mills at Eleuthria and the Brandywine, shoe manufacturing at HAnover, Copper and brass works and Iron works in the York Hills, LEmoyne,Columbia Reading ,Birdsboro,and Philadelphia. The isinglas works in Wrightsville were marginally important and "Extra Billy" Smith was, like STuart, always roqaming far afield from the core of the Confederacy to do a little plunder . SO Couch had the PA HOME GUARD, burn down the bridges over the Susquehanna and his theory was that hed force the Rebs up north. The forts were in Lemoyne right across the river from HArrisburg and really didnt do much good if the Confederates crossed over. Building the levies and forts did less than burning of the Wrighstville Bridge, which was the only way to cross save using bigass boat brigades. And with almost 100 K men to cross, LEe and his brigades were not gonna make it to HArriburg (which sat on the east bank). So the campaign, which was a means to get the "Peace movement" in gear so that the Confederates could sue for peace as a sovereign nation, didnt work out really as planned.
Couchs forts were mostly untouched except for one minor slir,ish . HEll, from the enclosed foto, you can see that the Lemoyne forts wouldnt do much for Harrisburg anyway.
The Civil War Album dot com is a good photo album of many of these site. Also the PA Civil War Museum in Harrisburg is actually a much betterinterpretive centyer than is the entie set up at Gettysburg. Gettysburg battlefield has always been a site of explaining who and where **** happened. (Its a necessary place to visit to get the sense of topography and scale of the battles) However, the why's of the campaign are lost to even the obsessed Civil War freaks .
The State Civil War museum does a far better job of boiling down the places and timelines to a series of reasons WHY many battles needed to be fought and in what order.
Heres a picture of the breastworks on which were mounted several long cannons set on plank skids . I have no idea what they were thinking.