The M577 command post vehicle is a member of the BAE Systems Ground Systems (previously United Defense) M113 series of full-tracked Armoured Personnel Carrier (APC) family of armoured fighting vehicles. Its correct US Army designation is Carrier, Command Post, Light Tracked M577.

The first four prototypes were built at the Detroit Arsenal under the designation of the XM577 and were conversions of the M113. Following trials, the XM577 was type classified in March 1963 as the M577, after the vehicle was already in production.

The original production M577 was powered by a petrol engine but the later M577A1 production vehicles were powered by a Detroit Diesel engine.

The M577A2 is a product improved version of the M577A1 and is provided with improved cooling, suspension system and personnel heating system. When fitted with the Reliability Improved Selected Equipment (RISE) power pack, the vehicle is designated the M577A3.

Total production of the M577 amounted to 1,152 units. This was followed by the M577A1 with 3,863 units built and the M557A2 with 2,417 units built. Some were also manufactured under licence in Italy under the leadership of Oto Melara. These are almost identical to the US vehicles, although early production Italian M577s had a two-piece side hull rather than a standard one-piece hull side.

The M577 is essentially an M113 series APC with a higher roof to the rear of the driver's position. The hull is of all-welded aluminium armour, which provides the occupants with protection from small arms fire and shell splinters.

The driver is seated at the front of the vehicle on the left side with the power pack to the right. The driver is provided with a single-piece hatch cover that opens to the rear. To his front and side are four M17 day periscopes with an AN/VVS-2 image intensifier or AN/VAS-5 thermal viewer being provided in the roof.

The power pack compartment is to the right of the driver's position and is fitted with a fire extinguishing system that can be operated by the driver or from outside the vehicle.

The air inlet and outlet louvres and the exhaust pipe outlet are in the roof and there is an engine access door in the front of the hull that hinges forwards.

The power train consists of the power plant (engine, transfer gear case and transmission) steering control differential, pivot steer, final drive and associated drive shafts and universal joints.

The crew enter the vehicle through the large power-operated ramp at the rear which is also provided with a door for emergency use.

The torsion bar suspension either side consists of five dual rubber-tyred road wheels with the drive sprocket at the front and the idler at the rear. The first and last road wheel stations are provided with a hydraulic shock-absorber. There are no track return rollers.

A rubber-track shroud on either side of the hull controls the flow of water over the tracks when the vehicle is afloat. The M577 is fully amphibious being propelled in the water by its tracks. Steering when afloat is the same as on land.

Before entering the water the two bilge pumps are switched on and the trim vane, which folds back onto the glacis plate when not in use, is extended at the front of the hull.

In the static role a tent can be erected at the rear of the hull to provide additional space for the command staff. A generator is mounted externally to provide power for the additional communications equipment installed.

Although the M577 was originally developed for use as a command post vehicle, it can also be used as a fire-direction centre, communications vehicle and a mobile medical treatment facility. The US Army and a number of other countries use the M577 for a variety of other roles such as ambulance.

Late in 1988, the prototype of the stretched M577A2E2 command post vehicle was completed. This has six roadwheel stations either side rather that five as on the standard production M577 vehicle.

In addition it features the external fuel tanks either side of the power-operated ramp at the rear. These were fitted to final production M113 series vehicles to provide greater internal volume as well as improved safety.

Other improvements included installation of the complete M113 series power pack, option of additional armour on the roof for enhanced protection against top attack weapons and the installation of an environmental control unit.

As of late 2007 the stretched M577 series remained at the prototype stage.

In 1990, the prototype modification kits for a new command post vehicle, then designated the XM1068 Carrier, Standard Integrated Command Post System (SICPS Carrier) were field tested by the US Army and prototype SICPS were used during Operation Desert Storm in 1991.

The conversion kit, mounted on the basic M577A2/M577A3 chassis consists of the following items:

• A new 5 kW Tactically Quiet Diesel APU mounted on the front of the vehicle

• A new tent extension carried on the top of the vehicle and attached around the vehicles ramp when the vehicle is deployed in the stationary position

• An AC/DC power supply and distribution system (wires mounted on the inner walls of the vehicle and external covered ports)

• An electronic equipment data distribution system (wires mounted on the inner walls of the vehicle and external covered ports)

• Mounting/stowage positions for the Army Tactical Command and Control Systems (ATCCS) hardware, which has two workstations

• A 10 m telescoping antenna mast

• A type M13 NBC system, with a ventilated facepiece for each crew member

As an option, an overpressure regenerative collective overpressure NBC system can be installed as can enhanced armour protection.

In July 1992, United Defense (now BAE Systems Ground Systems) was awarded its first contract for 162 SICPS kits to be used in depot conversion of existing M577 vehicles to the M1068 configuration. In June 1993 the US Army increased the kit quantity to a total of 330 units which have now all been delivered.

BAE Systems Ground Systems is also offering a command-post version of the Mobile Tactical Vehicle Light. As of late 2007 the Mobile Tactical Vehicle Light remained at the prototype stage.

Although originally developed as a command post vehicle, its greater internal volume means that the M577 can be used for a wide range of other roles. Germany, for example, uses it for artillery command and control, while a number of countries use it as an ambulance or medical treatment vehicle.

There are separate entries in the Armoured Personnel Carrier (Tracked) section for some M113/M577 users including Egypt and Germany as both of these countries have specialised versions of the M577 command post vehicle.