A defense mobile device for securing a door during shelter-in-place situations. The device includes wheels rendering it mobile and stops that, when activated, hold the device stationary. A panel has a ballistic core that resists bullets, a front face, an opening, and a cover positioned over the opening to overlay and enclose a door knob protruding through the opening. The front face forms, or has affixed to it, a writing surface. The panel pivots between a plurality of angled positions to facilitate writing and an upright position flat against the door. A locking rod, rotatably connected to the panel, pushes and pulls the panel between its angled positions and its upright position. A portal defined by a ballistic door viewer or viewport is located in the panel and permits viewing or observing through the panel. A release system is configured to deactivate the stop and enable the device to move.