Half-track Car M9A11-9

M9A1: General
Date of first acceptance March 1943 Total acceptances 3,433
Manufacturer International Harvester Corp. Crew 10 men
M9A1: Dimensions
Combat weight 21,200lbs
Height over .50cal MG 108"
Length with winch 249.06"
Width over mine racks 86.875"
Front tread 66.5"
Rear tread 63.8"
Wheelbase 135.5"
Ground clearance 11.2"
M9A1: Armament
Type Mount Ammunition Traverse Elevation
.50cal M2HB MG Flexible on ring mount M49 700 rounds 360°
+80° to -20°
.30cal M1919A4 MG Flexible on pintle mounts 7,750 rounds 360°
M9A1: Armor
Rolled homogeneous steel
Location Thickness Angle from vertical
Radiator louvres .31"
Windshield cover .625"
Sides .31"
Rear .31"
Hood top .31"
M9A1: Automotive
Engine International Harvester RED-450-B; 6 cylinder, 4 cycle, in-line gasoline
Horsepower Net: 143@2,700rpm Torque Net: 348 ft-lb@800rpm Fuel capacity 60gal
Transmission Spicer 1856 constant mesh, 4 speeds forward, 1 reverse
Steering Steering wheel
Brakes Hydraulic (Hydrovac)
M9A1: Suspension
Type Road wheels Track return rollers
Front: Semi-elliptic longitudinal leaf spring
Rear: Vertical volute spring
Front: Steel ventilated disc
Rear: 1 bogie/track;
4 dual/bogie
1 dual/track
Drive sprockets Idlers Shock absorbers
18-tooth front drive Spring-loaded at rear of track On front wheels
M9A1: Track
Center guide band type
Width 12"
Pitch 4"
Pitches/track 58 Track ground contact length 46.75"
M9A1: Performance
Max level road speed 42mph
Max grade 60%
Angle of approach With winch: 36°
Without winch: 40°
Angle of departure 32°
Max vertical obstacle 12"
Min turning diameter 59'
Max fording depth 32"
Cruising range ~200mi, roads
~320km, roads

The M9A1 resulted from the fact that White and Autocar could not keep pace with the demand for half-track cars, and was analogous to the M2 half-track. M9A1s differed in several respects from the M2A1, however. M9A1s lacked the side ammunition compartments, featured rear doors, the fenders on the M9A1s were flat in cross-section, and unlike the M2A1 the M9A1's body was the same length as the M5's, its personnel carrier counterpart. The M9A1 also never had the large fender-mounted headlights. International Harvester used rolled homogeneous steel armor on their vehicles, which allowed plates to be welded together, giving IHC's half-tracks a smoother appearance than the bolted half-tracks. The rolled homogeneous armor could also be formed, and IHC's half-tracks featured rounded rear corners, which contrast to the right-angled corners on the machines with face-hardened armor. Homogeneous armor lessened the chance of injury due to bullet splash and flying cap screws which could be dislodged when hit, but it was not as strong as face-hardened plate. This meant that the armor on IHC's half-tracks needed to be thicker than the face-hardened armor of the M2A1 to offer the same protection. The M9A1 was therefore fitted with heavier axles and hull strengthening components, but its performance still essentially equaled that of the lighter M2A1. No half-track cars M9 were produced, as the .50cal ring mount modifications had been approved before production began. The M9A1's length with the anti-ditching roller was 242.19" (615.16cm). A 2lb (.9kg) CO2 portable fire extinguisher was carried.




  1. TM 9-707 Basic Half-Track Vehicles (IHC) (Personnel Carrier M5, Car M9A1, Multiple Gun Motor Carriage M14, and Similar IHC Vehicles). Washington, DC: War Department, 21 May 1943.
  2. Hunnicutt, R.P. Half-Track: A History of American Semi-tracked Vehicles. Navato, CA: Presidio Press, 2001. Reprinted from Half-Track, R.P. Hunnicutt ©2001, available from Presidio Press, 505B San Martin Drive, Suite 160, Navato, CA 94945.
  3. TM 9-2800 Standard Military Motor Vehicles. Washington, DC: War Dept., 1 Sep 1943.
  4. Doyle, David. U.S. Half-tracks: The Development and Deployment of the U.S. Army's Half-track Vehicles, Part one. Ed. Pat Stansell. Delray Beach, FL: The Ampersand Publishing Group, Inc., 2014.
  5. Crismon, Fred W. U.S. Military Tracked Vehicles. Osceola, WI: Motorbooks International, 1992.
  6. Chamberlain, Peter, and Chris Ellis. British and American Tanks of World War Two. Frome, England: Cassell & Co., 2000.
  7. Siemers, Cary. "USA's Half Tracks." World War II Tanks & Vehicles and Advanced Squad Leader. 4 Jul 2001. 8 Aug 2001 <http://www.siemers.com/wwii/USA/Halftracks.htm>.
  8. Sola, Samuel, Vincent Bobkowski, and Kara Crocker. Weapon Mounts for Secondary Armament. Santa Monica, CA: G. O. Noville & Associates, Inc., April 1957.
  9. Track Data. Warren, MI: Track & Suspension Laboratory, Components Research and Development Laboratories, Research & Engineering Directorate, US Army Tank-Automotive Center, 23 June 1965.
Last updated 9 Dec 2023.
Questions? Comments? Corrections? Email me
© Copyright 2001-23 Chris Conners