Antitank cluster submunition
Antitank cluster submunitions are released from cluster munitions, either to immediately attack tanks and armored fighting vehicles, or to create a temporary minefield that only threatens these large vehicles. Antitank mines are not banned by the Ottawa treaty.
Direct attack submunitions
There are various types of submunitions that either immediately attack vehicular targets, or either self-destruct or otherwise render themselves safe. Direct attack submunitions exploit that the thinnest armor on a tank is normally on top of its turret and deck, so a guided weapon flying downward can hit the vehicle in its most vulnerable spots.
Many such weapons use first through third generation explosively formed projectile technology, all of which are highly directional. They may burn through the armor and spray molten metal or hot gas into the interior, setting off fuel and ammunition. They may also be designed to "squash" against the outer surface of the armor, transferring a shockwave that will cause the inner surface to spall, or break into high-velocity fragments.
Virtually all such submunitions are guided, some using adjustable fins to alter their glide, others using small rockets to maneuver, and yet others drifting by a parachute until they can "self-forge" into a hypersonic mass that shoots itself into the target.
The submunitions usually guide themselves, rather than follow a laser designator or other external commands. They may use various types of infrared seekers that distinguish the vehicle's heat emission from the ground; that heat difference will often persist for hours after the engine was turned off. Other types use extremely short wavelengths of radar, sometimes with an imaging and pattern-recognition capability.
Anti-armor temporary minefields
Submunitions may be intended to create a barrier to vehicular movement; indeed, in some situations, they may be made quite obvious, because stopping an enemy movement may be sufficient for a tactical situation. Lethal force is not always necessary.
Otherwise, the submunitions land, possibly adjust their ground position, and wait for a target. Different submunitions will use different sensing and damage mechanisms. A basic method is to have a pressure-sensitive fuze that will only go off when a heavy weight, much heavier than a human being, goes over them. Such a weapon may penetrate the usually thin bottom armor of a tank, or simply immobilize it by blowing off a tank.
More sophisticated submunitions, with explosively formed projectile mechanisms, can make side attacks from a distance. These may detonate when they sense the magnetic field of the vehicle, or discriminate using a combination of signatures, such as sound and heat.