Back in the day, we had the guilds. Each guild specialised in a form of war. There were the biker guilds who used bikes and trikes to power headlong into the thick of the fighting and attack with pistols, axes and lances. We had the transport guilds who used massive, heavily armoured land-trains to ferry resources and troops from A to B in relative safety whilst also being able to provide artillery support and a place to mount reconnaissance missions from. Then there were the aerial guilds with their gyrocopters and airships that provided reconnaissance and support for the ground troops. Finally, there were the warrior guilds; filled with formations of infantry. The guild-masters formed the lynch pin of each battle guild and contained all of the heaviest battle armour worn by the oldest and wisest squats of the home-world. The living ancestors were the advisors and provided psychic support where it was needed. There were, of course other guilds like the brewer's guild but those, along with countless others, were not part of the battle formations and are not really part of this discussion.
During the times of strife, we quickly learned a number of things...
... first, we discovered that the living ancestors acted as a beacon to the Tyranid hive mind. Almost as soon as the creatures entered our galaxy, the living ancestors were beset by visions of death and destruction. They became sick and suffered terrible fevers that wracked their bodies and caused them to ramble incoherently about the end of times. After only a few days, they began to perish and within a couple of weeks they had all gone to meet the ancestors. It was a terrible blow to us but it turned out to be a good thing that they had died because for a few weeks afterwards, the Tyranid advance slowed, as if searching for guidance. This gave us valuable time to gather our defences and prepare the Arks for departure.
Secondly, during the invasion we quickly discovered that the slow and cumbersome gyrocopters and airships were no match for Gargoyles and Harridans. They were quickly destroyed by weight of numbers; gargoyles clogging lift fans and scything through airship balloons with equal efficiency. Most of the aircraft were downed before they really had any time to get their shots off... so many Squats died without even taking a toll for their demise.
Thirdly, we hoped that the biker guilds would fare well in battle but although they were able to get into contact with the enemy quickly, their lack of armour and having to use one hand to control their bikes meant that they were quickly brought down by the hordes of hormagaunts and Tyranid warriors. Only the Exo armoured trikes of the guild-masters fared better but without armoured support, they too were overrun.
Fourthly, The land trains were particularly effective. Their tough armour, void shields and extensive arrays of anti personnel batteries, coupled with anti aircraft and anti armour weapons made them ideally suited for surviving the hordes of Tyranids. It was with huge regret that they all were sacrificed when the home-worlds were destroyed but they were pivotal in providing the time for the Arks to escape whilst drawing in countless creatures to their demise.
Finally, and most importantly, we learned valuable lessons about how we field our infantry. Small brotherhoods of troops fared poorly without the backup and support of other units so it was decided that the Imperial doctrine of using platoons was the best way to go. That way, we could have a mix of infantry and support elements that vastly improved survival rates. We also found out that the use of jump packs was suicidal and we lost far too many Squats due to lack of jump control and troopers becoming separated from their units. Our mole mortars were fairly effective but didn't have the rate of fire we needed and were overcomplicated; failing quickly and ending up useless to us. The ubiquitous thudd-guns were excellent at destroying the horde creatures and were another piece of equipment that we had to reluctantly leave behind. Fortunately, we were able to save all of the blue prints for all of our weapons of war (amongst countless other devices) so thudd-guns or even an advanced version of them are likely to be put into service in the future.
With infantry in mind, we were able to mix Squat and Imperial doctrines to provide support. With the bikers gone and the Exo troops being hard pressed, we discovered that the armoured Sentinels were just what we needed to plug the close support gap. They could take a beating from the smaller creatures and take a heavy toll with their heavy flamers and multi-lasers. They were even able to take down the larger beasts with their las-cannons and single shot missiles. Another Imperial practice we chose was the use of cavalry. Our giant badgers were able to attack just as hard as the troops who rode them to battle and were as keen to get into the fight as their brave riders. They were controlled using verbal commands and physically with the rider's boots so the trooper could use both hands to fight with.
Once the Ark ships had arrived in what the Imperials know as 'Runt Space', where the abhuman worlds are, we were able to make pacts with the inhabitants and begin to settle. Fortunately, these worlds were almost medieval in their technology so we could help the inhabitants by showing them how we build machines and mine the ore. Through our efforts we were granted the use of large areas of uninhabited land to settle and in return helped the beastmen to understand how our technology worked and how it could be produced. Unfortunately, they were not really ready for the advanced technology we could provide so we gave them weapons and technology that they could understand and were always nearby to provide repairs.
It quickly became apparent that our defensive capabilities were not up to speed. We had managed to salvage many weapons from the home-worlds but there were nowhere near enough to properly defend us. We couldn't turn to the Imperials for help because they were now in the books of grudge and deemed traitorous to us. Through our diplomatic relations with the beastmen, they introduced us to the blue men; the Tau. They were fascinated by our ion technology so we were able to trade with them. They had large manufactoriums on the star-ships that accompanied their trading fleets and, using the data we provided, were able to mass produce replacement weapons for us in the designs we wanted. Over a period of just a few months, our arsenals were replenished and our small support vehicles had been created. Some of the designs we provided the Tau with were adapted by them to improve efficiency; especially the Sentinels. The Tau's expertise with battle-suits enabled them to create a more robust design that fully encapsulated a wearer and turned it into an enlarged suit of armour, rather than a machine that was driven. It was the Tau's idea for us to replace our man-carried heavy weapons with drone mounted ones instead. That enabled the operators to get a better view of the battlefield and not be encumbered by heavy equipment. Originally they suggested that the drones should hover but we reined them in and said that we preferred the more practical design of tracked carriages. They were happy to oblige. In fact, our two races got on so well that some of our engineers and artisans were accepted into what the Tau called 'The Greater Good' and left with the Tau to work with them and share ideas on technology.
The early times on the abhuman planets were difficult but happy. After a while, we had settled in and had completed our underground dwellings and mines. Our manufactoriums were operational and were soon converting the ore from nearby asteroids into the raw materials for building our transports and war-machines. The beastmen introduced us to other abhumans; the Ogryn and Ratlings and we were able to share our weapons and mead with them in exchange for labour. The Ogryn were ideal to work in the heavy smelting plants and thoroughly enjoyed mining... even though they preferred hand tools to the laser cutting equipment. It didn't matter much because they were massively strong and were able to mine almost as quickly as the lasers so we were happy for them to be helping us. The Ratlings were a different matter. They were weak and small but they were excellent cooks, brewers and entertainers. The ideas that we shared led to the infamous 'Dominion Ale'... a brew so potent that only the abhumans could stomach it... any humans who tried it in the future were beset by hallucinations and in severe cases, were killed by it.
Yes, the early times were good.
We got back on our feet, made good allies and were establishing ourselves as a race again... but we knew that we needed worlds of our own and began planning our departure...