The MS-05B was the late production variant of the Zaku I and the first mobile suit assigned to combat units.[2] An improvement over the MS-05A Zaku I Early Type,[3] the B Type was visually identical to the A Type, but featured an improved cockpit design and better armor material.[2] Like its predecessor, the MS-05B’s power transmission pipes were all fixed and contained inside its armor. However, as the B Type saw wider deployment than the A Type, the flaws of this design quickly became apparent: since the power pipes took up most of its internal space, it was very difficult to improve its generator output or swap out parts. The structures of its limbs were also very complex due to the internalized power system. These problems would later be addressed by the MS-06 Zaku II series.[4] Its weapons included a custom machine gun, a 280mm bazooka, and a spike shield. It could also be equipped with the standard weapons used by the MS-06 series, including the 120mm machine gun and the heat hawk.[4]

• 105mm Machine Gun

A standard weapon for Zaku type mobile suits, this model is the initial type of the machine gun used by the Zaku series. A 100-round drum magazine is mounted on the right side vertically.

• 120mm Machine Gun

Another standard weapon for Zaku type mobile suits. It is a shell firing gun that does not require energy to be used, however its effectiveness against heavy armor is very limited. This model used a 100-round drum magazine.

• H&L-SB21K/280mmA-N Zaku Bazooka

The 280mm Zaku Bazooka was another weapon that could be equipped to a Zaku type mobile suit and it fires explosive rounds. It is primarily for anti-ship combat and displays its power in hit and run attacks. It can also be used against enemy mobile suits, but it is harder to hit a constantly moving target.

• Initial Type Bazooka

This early design of the bazooka featured a block ammo cartridge and a single exhaust port.

• 90mm Assault Rifle

A new model assault rifle that appears to be an upgrade of the MMP-80 90mm machine gun.

• Shotgun

A pump-action shotgun, it is of the same type as the one used by the MS-18E Kämpfer.

• 880mmRB-T27 Raketen Bazooka

A new heavy bazooka which features powerful rocket-propelled rounds, and improved targeting sensor with protective cover for aiming. It is fed by a 5 rounds magazine.

• Heat Hawk

A melee weapon, its blade was superheated to slice through the enemy’s armor.^[4] Its development was completed only after the MS-06 series began production.^[5] The MS-05 was normally equipped with the Type 3 Heat Hawk, which, despite being visually identical to the Type 5 Heat Hawk used by the MS-06 series, was not intended for anti-mobile suit combat and most likely designed for use against enemy ships and fighters. Some units, such as the Black Tri-Stars’ MS-05B, were later equipped with the Type 5. These had their output specifically adjusted for use by a MS-05.^[4][6]

• G-3 Nerve Gas Grenade Launcher

During the early days of the One Year War, the Principality of Zeon planned to drop colonies on Earth as weapons of mass destruction. Instead of using colonies from Side 3, they intended to capture Earth Federation allied colonies. To prepare these colonies, several Zaku Is were equipped with a G-3 nerve gas grenade launcher. These weapons launched rockets filled with G-3 nerve gas, a chemical weapon that could quickly kill every living person in a colony.

• S-Mine

Anti-personnel explosives fired from various locations on the Zaku’s body. They then explode in the air, raining down small metal shrapnels, killing approaching enemy soldiers.

• Knuckle Shield

The knuckle shield is a modified Zaku II shoulder shield carried on the arm, with the curve of the armor fitting over the mobile suit’s hand. One of the modifications is the additions of three spikes placed on the plate that rests in front of the hand. These spikes make the knuckle shield an effective bashing weapon. Darmac Barlow’s Zaku I in U.C. 0096 features a knuckle shield (minus the three spikes) with hard points to carry two 280mm Zaku Bazookas.

• Shoulder Shield

Originally a regular equipment for MS-06 Zaku II series, Darmac Barlow’s Zaku I in U.C. 0096 features a shoulder shield on each shoulder with hard points to carry two sturm fausts and three of the Gelgoog’s beam rifle.

• Heat Sword

A melee weapon originally developed for the Gouf line of mobile suits. Like the Zaku’s heat tomahawk, the heat sword’s blade is heated to high temperatures to increase its cutting capacity.

• MIP-B6 Cracker Grenade

Identical to those used by infantry, the cracker grenade is an explosive weapons designed to be thrown or launched by the MS and detonate after a set amount of time. The “cracker” breaks into several smaller munitions over a wide area.

• Sturm Faust

A simplified, disposable rocket launcher. As the warhead is not equipped with a guidance device, it is extremely hard to use the Sturm Faust to hit a moving target accurately. However, it is still a highly destructive portable weapon.

• Shield

The shield is a thick sheet of armor designed to take severe punishment that would normally destroy a mobile suit. Shields are also treated with an anti-beam coating to withstand several beam shots before the coating wears off. Typically, physical shields can only take so much damage before they succumb to the pressure and break.

• May, U.C. 0074: MS-05B is rolled out, three months after the MS-05A.

• Late October, U.C. 0077: The final version of the MS-05B, equipped with several devices and units developed for the MS-06, begins production. A total of 793 MS-05B units are produced before production is halted in favor of the MS-06 Zaku II.

• Late U.C. 0077: The MS-05B Zaku I is relegated to second-line duties, such as escorting transportation and supply fleets or garrison duty, as the MS-06 Zaku II’s production ramps up.

• U.C. 0079 (Early stages of One Year War): Zaku I participates in the earliest stages of the One Year War, including the One Week Battle, where they are used to launch gas grenades into colonies to kill inhabitants.

• May 8, U.C. 0079: A Zaku I guarding Zeon’s 67th supply depot in the Arizona desert is destroyed by an Earth Federation Forces MS-06J Zaku II Ground Type, piloted by Federico Czariano of the Semovente Corps, in what may have been the first instance of a mobile suit being destroyed by another mobile suit in combat.

• September, U.C. 0079: Gadem, a veteran Zeon pilot and captain of a Papua-class supply ship, resupplies Char Aznable’s squadron after the attack on Side 7.

  • His Papua-class ship is attacked by the White Base during the resupply mission.
  • Gadem uses his Zaku I to push out an MS-06F Zaku II from the ship to complete the mission.
  • Gadem, angered by the destruction of his ship, attacks the RX-78-2 Gundam with his Zaku I. Despite briefly engaging the Gundam, he is killed when his Zaku I is destroyed by the Gundam’s beam saber. 

• U.C. 0079 (Southeast Asia): A Zaku I-based MS-06V Zaku Tank, used as an engineering vehicle, helps repair the damaged Apsaras I. The vehicle is later stolen by Eledore Massis and Michel Ninorich of the Federation’s 08th Mobile Suit Team to escape a Zeon-captured village.

• November, U.C. 0079: After Zeon’s defeat at Odessa, Topp, a Zeon mobile suit team leader, retreats toward the Far East with her team.

  • They attempt to obtain food at a village that secretly houses anti-Zeon guerillas.
  • A battle ensues between Topp’s team and the guerillas alongside the 08th Mobile Suit Team.
  • Topp’s Zaku I is immobilized by a rocket from Shiro Amada. In desperation, she fires S-mines at a mob of villagers, killing them. Shiro then destroys Topp’s cockpit with another rocket, killing her.

• Battle of A Baoa Qu (U.C. 0079): Zeon mobilizes all available weapons, including the outdated Zaku I. At least one Zaku I is seen on the surface of A Baoa Qu alongside Zeon’s latest mobile suit, the MS-14A Gelgoog.