Years ago, I became aware of "Bolos" as a concept on one of those web forums dedicated to the fine art of versus debates. Over and over, matchups featuring "Bolos" would come up. Which sci-fi civilizations could withstand a single Bolo? Would you need more than a dozen to completely steamroll the 40k galaxy? It wasn't hard to understand what a Bolo was from context (a mindbogglingly huge autonomous tank), but everyone there just took it for granted. It wasn't until years later I found out they were from a shared universe book series (I had assumed some sort of RTS/tactics game like Total Annihilation).
To be honest, I seriously doubt that most of those guys had ever actually read these books. Few of these stories are so bombastic. In fact, in the early ones the tanks are almost immaterial to the story. They're arranged in ascending order of the capabilities displayed by the Bolos, not necessarily matching the very loose chronology ("Courier" would be one of the last stories, as the Concordiat is noted as being a thing of the past). In the last four, the Bolos themselves become characters in their own right, and sympathy for the machine creeps in, with the Bolos being either destroyed in the line of duty, or reactivated in decrepit states. Their adherence to concepts like duty and camaraderie humanizes them, but their singleminded pursuit of such reminds that they are machines. Is it better to struggle to be noble, or be created so? Will any of the future stories by other authors care when there are nuclear powered hundred foot tall tanks blowing shit up to write?
"A Short History of the Bolo Fighting Machines" (1967) - A frame story that contextualizes what the Bolos are, and the wide variety in their capabilities over thousands of years. The final sentence implies such a huge timeframe that there's unlimited space to write Bolo stories. Though some dates are given, chronology between the stories is almost non-existent.
★ "The Night of the Trolls" (1963) - You know the premise of Fallout 4? It's like that. Including the same twist. Luckily it has a secondary twist to deploy if you saw the other one. Was it as obvious in the 60s? Regardless, it's a fun action story, especially Hitmaning through a high-society party, even if the Bolos ("Trolls" in the post-apoc parlance) are kind of beside the point.
"Courier" (1961) - Retief Story. Bolo has even lesser role than "Trolls". Exact kind of trash lampooned by Star Smashers of the Galaxy Rangers. Below even The Legion of Space. RANCID ASS
"Field Test" (1976) - The activation of the first self-aware Bolo, told in a series of monologue-snippets from various characters, for and against. The scenario is absurdly perfunctory (the "People's Republic" is invading "Western Continent"), and even if the last line is decent, that can't save it from an overly-long buildup and another character who says "durn". Readable, at least.
★ "The Last Command" (1967) - Spaceport construction inadvertently activates a buried Bolo from decades earlier. Shedding ionizing radiation and unstoppable by conventional weapons, it mistakenly approaches a population centre and must be stopped. The story itself is just alright, but I love the ending.
★ "A Relic of War" (1969) - A technician arrives to deactivate an immobile Bolo in a frontier world village, but encounters resistance from the locals sympathetic to their Bobby. Another melancholic story, with a surprising reversal in store. Best story in the collection, but I struggle to say it's really great.
"Combat Unit" (1960) - Told entirely from the perspective of a Bolo, it struggles to escape after being reactivated without memory under hostile control. Comes closest to the "versus debate Bolo" in the whole collection. The ending is ambiguous about the Bolo's capacity for self-development beyond being a simple Combat Unit. Lacks drama compared to the previous two stories.