Should we trust Diaz's figures? They certainly seem more reliable than Cortes' claims. I think that his numbers are credible overall, but with a few caveats that help explain how the Spanish were able to survive.

Could Tlaxcala really field 50, 000 men. Well, the population of the state was around 500, 000 people. It might have been more, depending on how these details are calculated. 10% of the population would be tough, but seems doable. So the army may really have been that big.

However, the Spanish probably did not fight this army. At least not all at once. The first battle against the Tlaxcalans (sticking to Diaz's account of course) was a skirmish that involved only 3000 men, who did not fully commit to battle. The second battle began with 6000 Tlaxcalan soldiers, but included an ambush by forces under the control of Xicotenga. This is where Diaz's claim of 40, 000 warriors appears. Notice the sudden leap in numbers, from 6000 to 40, 000+, and I think this gives us great reason to be suspicious. Later, Diaz claims that the Tlaxcalans had assembled an army of 50, 000 men under five captains. This comment may reveal something about Tlaxcalan military organisation: that its army was divided into 'divisions' of 10, 000 men.

Interestingly, during the battle, Diaz notes that two companies did not join the fighting, which would mean only 30, 000 troops faced the Spaniards. This may reflect divisions in the Tlaxcalan hierarchy over how to respond to the Spaniards, with some favouring peace and even an alliance, while Xicotenga favoured war. This is a point that Diaz returns to later, making it clear that Tlaxcala as a whole wanted peace. After this, Diaz records a night attack that allegedly involved 10, 000 men, which seems like a return to more credible numbers. There is a lull in the fighting, but skipping ahead to the next incident, Diaz claims that Xicotenga had assembled 20, 000 men for another attack, which contradicts Diaz's earlier claims about Xicotenga commanding 40, 000 - 50, 000 men. Where did the other troops go? This attack never takes place though.

So, what exactly is happening here. Diaz's figures seem all over the place. I propose that Diaz had a good grasp of Tlaxcalan overall troop numbers. He spent some time in Tlaxcala along with other Conquistadors, and later fought with them in the Valley of Mexico, and this is likely where he picked up the 50, 000 number. However, he probably had no idea how many Tlaxcalans attacked the Spanish expedition at any one time, and just imagined that it must have been the entire Tlaxcalan army. It is far more probable that the Spanish never fought more than 10, 000 Tlaxcalan troops. I give this figure based on the organisation of Tlaxcala. Tlaxcala was divided into 5 allied states. Xicotenga commanded the troops from one of these (as Diaz himself may have indirectly noted), but it was unlikely that he had the power and authority to command them all. Indeed, Diaz's narrative all but confirms this, as he repeatedly noted Tlaxcalan disunity and that several commanders refused to fight.Furthermore, the 10, 000 figure fits better with Diaz's initial estimates of Tlaxcalan strength.

One further note. We must remember that there were more than 400 Spanish troops fighting against the Tlaxcalans. Diaz repeatedly notes that the Spanish brought allies from several Indigenous states, most notably Cempoala. I haven't estimated any figures. However, it is possible that there were several thousand of them. This would mean that Cotes's expedition was not that badly outnumbered, especially in the initial battles.