David Weber: Bolo!

MARK XXX BOLO (Magnificent) (3231):

Introduced on the eve of the Human-Melconian “Last War,” the Mark XXX was the direct descendant of the Mark XXVIII. The incorporation of counter-grav into the Mark XXX’s suspension and power train went far towards offsetting the mobility penalties increasing weight had inflicted on preceding generations. The Mark XXX incorporated still further improvements to the hyper-heuristic capabilities of the Marks XXVII-XXIX, new dual-ply battle screen (which was not only more effective against kinetic weapons but also capable of absorbing at least some of the power of almost any energy weapon and diverting it to the Bolo’s use), and a new and improved cold-fusion power plant. Weight dropped from the Mark XXIX’s 24,000 tons to 17,000 and normal speed increased to 115 kph. For very short intervals, the Mark XXX could divert sufficient power to its counter-grav units to achieve actual free flight at velocities up to 500 kph, but could not operate its battle screen or internal disrupter shields or fire its main armament while doing so.

MARK XXXI BOLO (3303):

Over the course of the thirty-third century, the galaxy slid with ever increasing speed into the maw of the “Last War’s” gathering violence, and Bolos after the Mark XXX did not receive the “type” names which had become customary with the Mark XV. The Mark XXXI was an enhanced Mark XXX with a main armament of one 200cm Hellbore (5 megatons/second). Secondary armament, though still referred to as “infinite repeaters,” consisted of two lateral batteries of six 20cm Hellbores each, and many small-caliber, hyper-velocity projectile weapons were retained for close-in defense and anti-personnel use. Indirect fire capability was degraded in favor of the assault role, for which purpose the Mark XXXI’s duralloy war hull was given an average thickness of 90 centimeters, rising to 1.5 meters for the glacis and turret faces. All secondary and tertiary weapons were mounted outside the “core hull” which protected the Mark XXXI’s power plants and psychotronics, and last-generation internal disrupter shielding was used heavily. The Mark XXXI retained the counter-grav assist of the Mark XXX and, despite a weight increase to 19,000 tons, could match the preceding mark’s speed.

MARK XXXII BOLO (3356):

The last Bolo whose year of introduction is known with certainty, the Mark XXXII was essentially a Mark XXXI with the added refinement of direct human-Bolo neural-psychotronic interfacing. Provision was also made for attachment of a counter-grav unit sufficient, under emergency conditions, to permit the Bolo to make an assault landing without benefit of transport. Offensive and defensive systems were comparable to those of the Mark XXXI. The Mark XXXII was the final version of the “standard” Bolo.

MARK XXXIII BOLO (?):

The last-and largest-Bolo introduced into service. The Mark XXXIII weighed no less than 32,000 tons and mounted a main armament of three independently-turreted 200cm Hellbores with a secondary armament of sixteen 30cm Hellbore infinite repeaters in two lateral batteries. Equipped with a very sophisticated indirect fire system, the sheer firepower of the Mark XXXIII was a reversion to the old siege unit thinking, though it was normally referred to as a planetary siege unit, not merely a continental one. No one knows how many Mark XXXIIIs were actually built, but official planning called for them to be deployed in independent brigades of 24 units each. Despite the increase in weight, speed remained equivalent to the Mark XXXI, and the Mark XXXIII’s internal counter-grav could supply the assault landing capability for which the Mark XXXII had required an auxiliary unit.

General Armament Notes

In addition to the weapons listed, all Bolo secondary armaments include small-caliber high-velocity projectile weapons for close-in defense and anti-personnel fire. All Bolos after Mark V also mounted multiple-shot flechette anti-personnel “clusters” with progressively heavier flechettes.

Any Bolo secondary gun with anti-armor capability was always referred to as an “infinite repeater,” although the term originally applied only to a small– to medium-caliber projectile weapon with a high rate of fire and large magazine space.

Like most of their other weapon systems, the vertical launch system missile outfits of Bolos evolved tremendously over the course of the Bolo’s design history. The original Mark III VLS consisted of only 60 non-reloadable cells, although more than one missile might be loaded per cell if they were small enough. By the time of the Mark XIX, the VLS consisted of reloadable, magazine-fed cells, and all future Bolo VLSs followed that pattern. The term “light” or “heavy” used to describe a VLS refers to (1) the number of cells (and thus salvo density) and (2) the VLS magazine capacity, not to the weight or size of missiles thrown.

The breech-loading mortars fitted to most Bolos after the Mark XIII might be considered automatic weapons, as their rate of fire averaged from 8 to 12 rounds per minute. The Mark XXXIII’s 15cm BLMs had a maximum effective range of 3,000 meters; the 40cm BLMs of the Mark XXIX and Mark XXXIII had a maximum effective range of 9.75 kilometers.