There are any number of branches and departments within the Departmento Munitorium (DM); some of these are mentioned in the various IA books by FW, some are alluded to in the Imperial Guardsman’s uplifting primer. A couple have been mentioned in the background for the Devos IV campaign.
Each of these departments sees its own work as vital and probably as at least as, if not the most, important thing in the ongoing work of the Imperial war machine. Doubtless some departments see adherence to their own procedure (dogma) as more important than the outcome of any one campaign or war being fought by the Imperial Guard.
At the very highest level, there may well be recognition that the purpose of the departmento is to service the needs of the combat arms (IG and Navy) and ultimately even the sacrosanct process of the depratmento itself must come second to the needs of the service.
However, The Departmento is big. It is huge. It routinely deals in millions. An army like the Sabbat Crusade army or armies is quite likely to reach a hundred million or more.
One of the problems with it, as I have alluded to before, is that it is, on a strategic scale, not at all agile or responsive. It might take generations to set up the supply lines for something like the Armageddon wars. But once in place, the flow of men and material to the warzone is going to be much easier to divert than to stop. There are places within the Imperium where the economy is permanently on a war footing; which war becomes irrelevant as the constant flow of rations, fuel and ammunition, coupled with the pulsing movement of IG regiments lends a Grimdark feel to a lot of the major supply routes.
One can imagine all of those oft mentioned endless streams of pilgrims not quite meeting the gaze of the endless stream of soldiers going the other way.
The differing departments (Dept XA42 – Death Korps of Kreig Officers Careers) all have pressures, whatever they might be (Dept 349uH7 – Rough Rider mounts rations supply to the Cadian Gate). And therefore (Section 44 – Engineering spares for Bromhead pattern tanks) there is a particular tension when it comes to things like booking space on freighters (Branch 3 – space on Imperial Navy shipping leaving Agripinna). They like to think that they are all pulling in the same direction, but also they all want their particular office to be seen to perform well, even at the expense of others. It becomes easy to imagine DKK formations without officers, overwhelmed with the tank spares for their cavalry mounts because someone in Section 44 has called in a favour from his counterpart in Section 3. Section 44’s quota has been filled, where’s the problem ?
As well as this type of supply there are also the Labour Corps and Engineering Corps raised for each army despatched. These could be quite small, or quite large, depending on the perceived scale of their task at the time the army was raised. These bodies of men would be ‘on the strength’ ie entitled to draw rations from the DM. The greatest function of the DM Labour Corps (which might just be one man with a data terminal and a cheque book, organising private contractors) is to move all of these supplies from their point of origin to their point of issue to the user. So, for example, this might be Death Rider officers from Kreig to Armageddon. Quite a journey, which itself requires a complex logistics plan in order to be successful.
On the ground, then, the deployed part of the DM is going to be represented at the mightiest level by a codicer or archivist from the department (for the 72AG on Devos IV, this is Comptroller Bellormus). Whilst this individual has great power (he can call on off world resources and raise local contracts), he also has huge weight of responsibility. All those officers careers are not going to be run remotely from Sector Command; they will be run locally by the Comptroller’s office. These records, like almost all the records from the campaign will not be transmitted by astropath (you can fax the Encyclopaedia Britannica, but it’s easier to fed-ex or DHL it), but packed up and conveyed back to the archive at the end of the war.
In theatre, the labour corps will undertake tasks such as Stevedore for the materials arriving from Orbit and transport to the second line depots. They will undertake third line repair tasks and maintain and service rear area accommodation. They are the graves registration service, such as it is. They are the menders of uniforms, the packers of munitions, the selectors and creators of ration packs, medicae supplies and morale-picts. If you get a ploin or lho stick at the front line it has been through their hands, possibly literally. There is a vast swathe of stores to handle and people are more adaptable than any machine. The Labour Corps is not just a horde of the otherwise unemployable in dungarees; it is a body containing many trades, employing any number of skills and techniques in order to keep a vast and incredibly diverse army in the field.
The Engineering Corps will undertake tasks such as the construction of airfields, roads and railways. If needed, fortifications. Their remit might include extrapolating the infrastructure and labour corps requirements from the military plan. They are enablers on a grand scale; as the Imperial Guard spread across a planet, hostile or not, the Engineer Corps follow on behind, creating railways, supply depots, desalination plants, airfields, orbital drop sites, fortresses, sea ports, boats, trains, diggers, prime movers, promethium processing plants (vehicle fuels and flame weapon fuels are different). They build and in order to do so must create processing and batching plants for aggregates and concrete materials, probably foundries and manufacturae as well.
Additionally the in theatre DM presence will organise, track and to a certain extent, control, the manpower not only of the Labour and Engineering Corps, but of the IG deployment as well. They will account for every brass button and shoelace issued. And set the level of requirement (ie, will everyone live in a tented camp or NBC proof bunkers ?) depending on circumstances. The IG will then, by and large, have to get on with it. The regiments will cope with what they’ve been given.
This is not to say that the IG is being choked by bean counters. We know that, for instance the Taros campaign failed because it was under resourced. However things like Valhallan Regiments deploying without sufficient small arms will be due to the vagaries of the warp, or some other supply chain difficulty, rather than the malicious application of an inadequate equipment scale of issue.
Within a main supply route, commodities are likely to be fairly easy to come by; however they will be intended for a specific task or user and if they need to ‘re-purposed’ then authority for this must come from someone of the correct grade. Which inevitably is higher than anyone the hard pressed user has available.
For a place like Vraks, it is likely that it wasn’t an arsenal world to begin with and perhaps was not actually chosen as such; it was a rock ball with an atmosphere on the supply chain to a war somewhere. So when that war ended, there was a lag in getting the message back to where the supplies were coming from. So those items already en route were halted at Vraks and used equipment from the front was back loaded to Vraks as well. Lo and behold the tiny shrine world had a new purpose as an imperial arsenal.
The DM, off world, exists to establish and maintain supply lines along a general axis to service a warzone. Off world, the DM is answerable to the High Lords of Terra for keeping the Emperor’s armies and navies in a fit state to fight the Emperor’s wars. In practice, this is a never ending treadmill of conflicts, so for the off world DM, only the point of delivery for all their efforts changes, everything else is more or less constant.
In theatre, they exist to undertake all the tasks required to keep an army in the field and allow that army to fight and therefore fulfil its role. In theatre, there will be DM representative who enjoys roughly analogous seniority as the commander’s Chief of Staff. He is the man who will run the war for the Commander from Orbit up to the second line of the battle front. And he will have resources commensurate with this task.
What this means to a new regiment is that once it marches up the ramp to its first deployment it becomes merely a T card in a DM wall chart; however, once it is part of an actual deployment, it potentially has the resources of the best part of the Imperium behind it.
Once the DM has a supply chain set up onto a world, there is rarely any question of whether or not that world will fall to the IG; consider Balhaut. There was never really any doubt about the outcome, it was just of level of resources to be spent (in terms of IG Battlegroups) in order to achieve the objective. The Warmaster had made Balhaut the focus of his crusade and thus it was conquered. A world can be lost again soon afterwards, once the DM has shifted its focus (and supply chain) elsewhere.
The Taros Campaign suffered from a ‘closed book’. The expected resources were allocated and ‘the book’ was closed. Hence when the Tallarn regiments began to suffer from an unexpected level of attrition, there was no adequate avenue to pursue to reinforce the army (here we see the DM’s glacial timescales jeopardising real time military operations). What 4* Gen Zhukov has achieved on Devos IV is to keep the OH interested in the campaign they instigated in the first instance – he has by turns ignored and then indulged the Inquisitor send with him – latterly providing a surfeit of witches and thus getting the OH to influence the DM, getting him the resources he wanted but would never be allocated without some form of outside influence.
 Just don’t go there, OK ?
 The supply of las gun cells according to the manifest is more important than answering an urgent operational requirement from one regiment. Who cares if the Corbanian 1st end up throwing stones when the small arms ammunition department have the whole of the IG to service ?
 Ie are being supplied from the official supply chain. Whereas members of religious missions might only be supplied by negotiation.
 One instance of separation of interests where the High Lords can see the benefit of 3rd party management.
 It was resourced adequately for what they thought would there, rather than what they ultimately encountered.