This trial is testing a neuro-mechanical gait assist (NMGA) device to improve walking for Veterans with hemiparesis after stroke. The NMGA device is a knee-ankle-foot-orthosis with a motorized knee joint and surface neuromuscular stimulation of plantar- and dorsi- flexors, vasti and rectus femoris. The device is controlled by a finite state controller (FSC) which coordinates feed-forward control of tuned stimulation patterns and closed-loop controlled knee power assist as needed to control foot clearance during swing and stability of the knee during stance.