To remedy the situation, one of McClellan's first orders upon taking command was to greatly expand the defenses of Washington. At all points of the compass, forts and entrenchments would be constructed in sufficient strength to defeat any attack. One area of particular concern was the region of Maryland south of the Anacostia River. Confederate artillery floated across the Potomac in secret and mounted south of the river could threaten the Washington Navy Yard and Washington Arsenal, both of which lay at the junction of the Potomac and Anacostia Rivers.