What a time it must have been to be alive when Procopius wrote The Wars of Justinian. To have lived during Chosroes I sack and razing of Antioch in 540 — not to mention the population's deportation to Persian Mesopotamia —, the brutal Gothic sack of Milan in 539, the three sieges — and near razing — of Rome, and to have witnessed the "revival" of a "complete" Roman Empire are just some of things Procopius was "fortunate" to have lived through. Add to that the Plague of Justinian, the denudement of North Africa, the Balkans, and Italy of its population and prosperity, and you see why Procopius lived during one of the most transformative eras of pre-modern history. Fortunate, of course, is the wrong word, because life during those years must have been absolutely terrible and I am grateful that I get to witness it as a very, very distant observer.
If there is an ancient source that tells us the true story of the collapse of Roman society it's Procopius, despite his critics. True, The Wars of Justinian is very nearly purely a military history and lacks the biting political insight and meta-analysis of Thucydides and Polybius. It makes up for the lack of explicit political insight by having plenty to read "between the lines" thanks largely to Procopius' attention to detail, relative accuracy, and what reads as a commitment to the truth.
On the topic of Procopius and the truth, we know that he was not entirely honest on the background politics. We know this because he says so himself in the Anecdota (i.e. The Secret History). Even so, The Wars of Justinian is a much better book than the Anecdota from the perspective of accuracy and detail, even if he couldn't be completely honest as to the imperial politics of the time — for the most part, he abstracts from what he can't be completely honest about, rather than be dishonest about it.
Coming back to the idea of Procopius being a better source than any on the collapse of the Roman Empire, it seems strange at first to make this claim because The Wars of Justinian talks very little about events during the 5th century. There is some detail when he gives backgrounds on the Vandals and the Goths, but these details are sparse and not even within the magnitude of being a detailed history of events during those years. So, how could Procopius be a source on the collapse of the Roman world? Because there's a case to be made that the collapse happened during the 6th century, not the 5th.
I'm reminded of Michael Kulikowski's Late Roman Spain and Its Cities, a very deep archeological and historical study of the Iberian peninsula between the 4th and 7th centuries. What you see archaeologically is a great deal of continuity in classical culture in Spain, although it had withered to some extent and was going through a similar transformation as much of the rest of the Mediterranean — the decline of the classical city. And like most things in history, the transformation happened over centuries of time. But, if there is one breaking point that we can see in the archeological evidence, it doesn't happen in the 5th century. It happens in the 6th, with the arrival of the Romans and the creation of the province of Spania. Procopius reinforces this narrative.
The reconquest of the West may often be seen through the filters of former Roman glory, but it was not the old Roman world that Justinian sought to rebuild. The government he imposed on re-conquered Italy and North Africa was not a benevolent Roman government on Roman citizens, but rather the imposition of a tributary system that sucked the life out of the entire empire. Take notice, for example, of their decision to impose a tax on Italian cities not just for the present, but also to repay their "betrayal" in having accepted Gothic rule at all. Of course, this tributary system was not efficient. The Roman government under Justinian was not an efficient tyranny. Rather, it was a disintegrating government with rampant corruption, where much or most of the tribute exacted never even made it to the imperial coffers.
Perhaps one of the most telling events in The Wars of Justinian is the story of Bessas, the Roman commander of the garrison defending Rome during the second siege, in 546. Bessas monopolized the distribution of grain and sold it to the rich at monopoly prices, causing widespread famine. Procopius muses that Bessas longed for the siege to be as long as possible, so that he could make more profit. Does this sound like a government that cares about the people it conquered?
Likewise, consider the fate of North Africa. Conquered almost by accident, it the sense that Belisarius' tiny 15,000-man army could have been defeated at any point had the Vandals not been suffering from their own political fracturing, the North African cities at first welcomed the Romans as liberators. If only they knew that within a decade or two, North Africa would be squeezed dry of revenue, depopulated through war, plague, and starvation, and largely governed by individuals seeking to maximize the revenue flowing into their own pockets. Procopius, who saw it with his own eyes, describes North Africa's fate as very nearly being a wasteland as a result of Roman rule (this is from The Secret History). Italy's future was very much similar, as a decade and a half of war, misrule, and starvation led to massive depopulation and the literal destruction of entire cities. Procopius estimates that 300,000 people were killed in Milan — a definite exaggeration, but a cue as to the scale of the disaster.
While the Romans reconquered North Africa and Italy, the eastern provinces were ravaged by Persian and Saracen armies. The Balkans were invaded and raided by Huns, Gepids, Lombards, and others. Cities were sacked and razed, populations were massacred or enslaved. Oftentimes, namely in the Balkans, entire tribes were settled within Roman lands. Why? Because Justinian had stripped the frontier of its armies so that he could fight his wars of conquests, and the armies that remained were poorly paid and poorly led. To understand the why, you have to read The Wars of Justinian and The Secret History together; for example, you only learn about the defunding of the limitanei (Rome's frontier forces) in the latter.
It's easy to blame the barbarians, though. What about the commanders who refused to put up effective resistance? Well, then again, their soldiers weren't being paid. In fact, other than top commanders, even the leadership was oftentimes unpaid. No wonder they defected to the enemy so often. Likewise, when your imperial leadership has a history of fabricating crimes to convict the rich and steal their wealth, what incentive do you have to be a functional arm of the administration? None. Even if you are especially noble, how can you defend Italy against Totila when Justinian can't provide you with an effective field army? And how can you defend against the Persians when more and more soldiers are fighting in the west?
Procopius' Wars of Justinian is not a history of the apogee of Roman revival. It's a history of a dying, rabid animal in its final death throes. And it is primarily a military history, and as a military history it is quite excellent, but the amount of detail gives you something more. It gives you the sense not of imperial renewal, but of a resource-rich ship that's slowly sinking and where the crew is now more focused on getting their share of the spoils than on pulling ahead as a team — because playing as a team isn't rewarded, just look at the life of Belisarius, a man who gave it all for his empire and was mistreated by his political masters in return.
This particular translation is fantastic. Kaldellis does a very good job of modernizing the English. He also does a great job of minimizing the footnotes, but also using the footnotes more strategically. As mentioned, The Secret History is like the B-side to this A-side; or, more accurately, it's the seasoning that brings out the flavor of the protein, the protein being The Wars of Justinian. Kaldellis connects the two books in his footnotes, such as when Procopius gives an alternative, more accurate explanation for an event in the other book (because The Secret History was published after the deaths of Theodora and Justinian, so those political secrets no longer had to be kept at the risk of execution). I do recommend reading both, and furthermore I recommend reading The Wars first and The Secret History second.