configured for maximum flexibility. No railgun main armament was mounted, but the 60mm infinite repeaters were upgraded to seven guns per side, and a heavier point defense battery intended to provide cover for other friendly units and to protect the Bolo itself when operating in counter-battery mode was fitted. One-man crew; 238 tons; speed roughly comparable to the Mark V’s.
MARK VII BOLO (2163):
The Mark VII was a “heavy” Bolo, whose introduction inspired the first use-though still unofficially-of the term “siege unit.” It had the same electronics fit as Marks V and VI, but its main direct-fire armament was one 200mm railgun backed by fourteen heavier (75mm) infinite repeaters. The Mark VII’s heavy missile load was biased towards the bombardment function, but it was equally capable of operating SAMs in the area defense role. This vehicle has a very heavy layered durachrome war hull (120 millimeter) and required a two-man crew, rather than the Mark V’s and VI’s one-man crew, but in the VII/B the second crewman served solely to control the indirect fire armament. In later models, the second position was upgraded to a dedicated air-defense/missile intercept function. Weight was approximately 348 tons in the Model B, with a maximum road speed of 40 kph and a maximum cross- country speed of 30 kph. (The Mark VII was never very fast, but its sheer mass meant most terrain features tended to crumple when it hit them and so did not slow it as severely.)
MARK VIII BOLO (2209):
The Mark VIII was the next-generation “main battle” (or “standard”) Bolo. Main armament remained a railgun, though muzzle velocity increased still further and projectile size fell slightly (to 170mm), but this Bolo marked the first appearance of energy-weapon (laser) infinite repeaters. (By the time of the Mark VIII, any Bolo’s secondary battery had come to be referred to as “infinite repeaters” whether or not they fired actual projectiles.) Although the new laser infinite repeaters were actually marginally less effective than the last-generation railgun infinite repeaters on an energy-transfer-per-hit basis, mass per weapon fell, and the shift meant magazine capacity for the secondary battery was no longer a design factor. Missile capability was limited to the SAM and point defense role, but the Mark VIII received four hull-mounted 150mm rapid fire howitzers to compensate. The VIII/B was fission-powered, with solar charge backup capability, a one-man crew, and a weight of approximately 225 tons. Improved power train and suspension permitted a sustained road speed of 65 kph and short-range “sprint” speeds of up to 85 kph, but maneuverability at high speed was poor.
MARK IX BOLO (2209):
The Mark IX was the next generation “siege” unit, introduced simultaneously with the Mark VIII as companion vehicle. The main battery railgun was suppressed in favor of additional missile power and four high- trajectory 180mm howitzers in two back-to-back twin turrets. Further improvements in electronics allowed the Mark IX, unlike the Mark VII, to be crewed by one man. Weight was approximately 400 tons, and maximum road speed for the IX/B was 57 kph.
MARK X BOLO (2235):
The Mark X saw the first appearance of an energy main armament (laser cannon) in a Bolo. As with the laser infinite repeaters of the Mark VIII and IX, the new system was actually less destructive than the one it replaced on a per-hit basis, but it required no magazine space. The Mark X was fission-powered and carried laser infinite repeaters, and approximately 1/3 of the preceding Mark IX’s gatling closein anti-missile and anti-personnel weapons were replaced with multibarreled flechette-firing railguns in independent housings. The Mark X carried only self-defense missiles and no high-trajectory indirect fire weapons and required a one-man crew. Later models of this mark had sufficient computer capability and flexibility to begin use of pre-loaded computerized battle plans, requiring human intervention only when unanticipated tactical situations exceeded the parameters of the battle plan. The Mark X, Model B’s battle weight was 350 tons, with a maximum road speed 70 kph.
MARK XI BOLO (2235):
The Mark XI was essentially a backup, designed to cover the possibility that the Mark X’s laser main armament might prove impractical in service. Main armament was one 18cm railgun firing depleted uranium long- rod penetrators in the anti-armor role and a wide range of cluster, incendiary, chemical, and fuel-air rounds against unarmored targets. Otherwise, the Mark XI was identical to the Mark X. This vehicle remained in service longer than might otherwise have been anticipated because the projectile-firing capability of its main gun proved extremely popular with tacticians.
MARK XII BOLO (2240):
This was the first true “continental siege unit,” designed for strategic indirect fire with VLS cells capable of handling missiles with intercontinental range. The Mark XII was capable of MIRVed FROB attacks and of engaging orbital targets with hyper-velocity surface-to-space missiles. Main anti-armor armament was deleted, but the Mark XII was equipped with extremely capable anti-air/anti-missile defenses (in effect, it was an area defense system, as well as a bombardment unit). The vehicle was normally mated with a BAU (Bolo Ammunition Unit), a Mark XII with all offensive armament deleted to provide magazine space for multiple load-outs for the Mark XII’s missile batteries. Although the Mark XII continued to carry a one-man crew, it was primarily designed for pre-loaded computerized battle plans. Weight was 500 tons, with a road speed 50 kph.
MARK XIII BOLO (2247):
The Mark XIII was essentially a Mark XII with main anti-armor armament restored. Although the main gun ate up almost 25 percent of the tonnage dedicated to magazine space in the Mark XIII, the Mark XIII’s bombardment capability actually slightly exceeded that of the Mark XII with only minimal overall weight increases. This was made possible largely through improvements in fission technology (allowing a smaller power plant) and the first use of a flintsteel inner war hull under a much thinner durachrome sheath. The Mark XIII/B’s weight of 565 tons held fairly constant in all models of the mark. Road speed was 50 kph in the XIII/B, rising to 75 in late-series models as suspension and power train improvements became available.
MARK XIV BOLO (2307):
The Mark XIV replaced the never entirely satisfactory laser “main gun” of earlier marks with the far more destructive “Hellbore” plasmagun. This 25cm weapon, originally designed for the Concordiat Navy’s Magyar-class battlecruiser’s main batteries, had a half-megaton/second energy output and, unlike the earlier Bolo laser cannon, was a marked improvement over any kinetic weapon of equivalent mass. In other respects, the Mark XIV was a “standard” reversion to a generalist design, made possible by advances in mag-bottle technology (which finally made fusion power a practical alternative to fission in Bolo design) and acceptance of a lighter indirect fire capability. Anti-missile defenses were now sufficient to render strategic bombardment impractical, so indirect fire was limited to tactical and theater applications. This permitted the use of smaller missiles which, in turn, allowed an increased magazine capacity without weight penalties. Even so, the Mark XIV/B was 28 percent heavier than the Mark XIII/K it replaced, although further power train and suspension upgrades prevented any loss of maneuverability or cross-country performance. Gradual improvements in sensor fits and fire control systems kept this mark in front-line service for approximately 90 years. Tactically, primary reliance now rested firmly upon pre- loaded computerized battle plans, but a single human crewman was routinely carried to respond to unanticipated threats. The Mark XIV/B’s weight was 728 tons (rising to 900 in late-series models), and road speed hovered between 60 and 75 kph over the life of the mark.
MARK XV/BM BOLO (Resartus) (2396):
A quantum leap in Bolo technology, the Mark XV was the standardbearer of the Concordiat during humanity’s greatest wave of interstellar expansion. Very few non-human species encountered during this period could match the Mark XV’s capabilities; none could exceed them. This was the first Bolo which did not require an onboard human crewman, due to advances in cybernetics and secure communication links (first short-range subspace com capabilities), which permitted increasingly sophisticated computerized pre-battle planning coupled with unjammable remote human control to correct for unanticipated problems. Main armament was one 25cm
