Vaes Dothrak. Esso.
No one knew how many Dothraki Screamers there were in the world, but they did know who commanded the biggest tribe and while that was not Khal Moro he would soon be one of the most famous warriors in Dothraki history, once he had liberated the only city that no Dothraki had ever sacked since it was their own. Vaes Dothrak had never before been conquered by outsiders and when Khal Moro killed the invaders he knew that for many generations to come his name would be told to the children in story for many generations to come. Men would name their sons after him and women would think of him as those sons were made.
That he would reclaim Vaes Dothrak was in no doubt in his mind. The invaders had built walls and they had men on those walls, and while in other battles this would be an issue for the Screamers, the foreigners had left a gap in their defences. Khal Moro was no fool, he suspected that this might have been done on purpose, but it wouldn't matter if he managed to charge enough of his warrior through the gap. Once inside the city it wouldn't matter how tall or strong these walls were. The invaders would be slaughtered and any who weren't would be made slaves.
Little he did know that the leader of the invaders was hoping he'd do just that. Khal Moro knew nothing of mines or mortars or heavy weapon emplacements, he could not imagine what he was about to charge into, and he wouldn't live long enough to learn from what was about to happen. All he could do was lead the charge because even if he had understood how poor his chances of victory actually were it didn't matter. Even if he backed down then one of his own warriors would simply challenge him, thinking him a coward and once that happened it would only be a matter of time before some challenger did end him and the new Khal would simply charge on the city in the hopes of earning glory.
With his path fixed Moro signalled for the charge. To begin with, it went well, the Screamers moved with greater coordination than was to be expected, and their morale was high, right up until they rode straight into the minefield. The first death was that of a blood rider who in his eagerness had set off slightly before his Khal's horse had begun to move. His eagerness was not rewarded as the blood rider become the first man from this world to be killed by a landmine, which scattered parts of him across the grasses.
The horses, bred and trained to carry warriors into battle, did not understand what was happening and began to panic as more mines were encountered and even with their riders doing their best to keep their mounts under control, this only resulted in more losses as the minefield was wide. Had the charge remained more organised the mines would have been less effective. Alas for the Dothraki they simply didn't know how to cope with what they saw as magic.
This proved to matter little in the wider scope of the battle as by now the Screamers had entered the range of the mortars which began to rain death upon those riders who had grouped too closely together rather than scatter. Khal Moro tried to keep things organised, but the momentum of the charge kept many of them moving towards the city as if reaching it would offer some sort of safety.
Quite the opposite was true was while the fire from laser rifles wouldn't be accurate given the distances involved the invaders had other weapons with much greater range, and these further depleted the ranks of riders until they began to really scatter. This was when Moro realised that his tribe was doomed. Even if they retreated with enough Screamers to do battle again he would be blamed for this defeat since he was the leader and as such he would not be Khal for much longer.
Now he could only die in battle, he charged and died seconds later when he entered the effective weapon's range of the laser rifles held by the invaders and took dozens of shots in a second. A single laser blast could be deadly to an unarmed human and he was struck by more than ten so what was left of him would only make a meal for the scavenging beasts. The bloodrides, those who should have avenged his death were soon to join their leader as the deadly red beams brought an end to their lives.
In the days to come, the once-mighty khalasar would fracture into many smaller warbands and many slaves would flee, and while the invaders had no desire to battle with the khalasars out in the great grass sea the disorganised bands that had no direction and poor leadership would be easy prey for their metal machines. In time other Khals would come to try to reclaim the city and they do would also suffer an overwhelming defeat while the invaders only grew stronger.