Iron was not as prized as bronze back in those days. And there were bronze triggers.
Iron was also not much of a big deal, as people make farm tools out of it.
I make no claim on training standards. Take a different perspective, training for violence can start in early childhood and exclude other specializations. That's quite typical for a nobility of warriors, be it Spartans, later day samurai (not ashigaru), Spartans or European knights (not sergeants). There are full time specialists, ther are trained specialists and there can be little trained supporters.´The Spartan army consisted mostly of light armed helots who supported the Spartans, perioici and later mercenaries or freed former helots.
In Eastern Asia the Chinese early on invented the wheelbarrow. It's logistics that make or break army size and in Europe you have to take into account the prodigous amount of grain consumed by riding and transport animals during a campaign. This results in a corresponding army size and campaign structure. Reduce per one horse and kep in mind that a rider needs several horses and you get at least 4 infantrymen per horse, not even conting all the mules and donkeys. Thus a typical European army that was heavily dependent on equids could more than quadruple with Chinese wheelbarrows.
It's likely that there exist wrong self perceptions and prejudices on all sides of this landmass.
Let's try to find some details, how could 600,000 men communicate to do something in an organized manner?
How did they feed? The handcart idea was tried in the American West as well and did not convince.
"Primitive iron was hard but brittle, making it a poor choice for making weapons. Unless, of course, we're talking about arrows and bolts: no need to care about brittleness then."
I guess that you've never tried to fire a crossbow, or make an axe/knife/bodkin out of anything, but the reason that iron took over the world was that it made better weapons and tools! Also, the far greater mass of an iron crossbow bolt will GREATLY reduce it's velocity and effective range! (it's very easy to make excellent bolts out of bamboo) As with all things having to do with Chinese history you have to see it more as propaganda than history!
As to the HUGE numbers of Han crossbowmen, think of (first) it's much easier to teach an untrained peasant to fire in un-aimed Napoleonic volley fire, than teach them how to shoot a bow (why the Mongols won so easily)! and that being said try to imagine that (volley fire) from "thousands" of crossbowmen with the aforesaid iron bolts, it would be tons and tons of iron as a gift to the enemy who would only have to stand back out of range and return fire with bamboo bolts!
The armies of the time must have used tens of thousands of crossbow-bolts, and the shift to the use of iron for these would have made immediate economic sense. The interesting question is: why did bronze continue for so long to be used for tips? Excavators have often expressed mystification at this. An explanation is suggested by comparison of the bronze and bronze-iron crossbow-bolts in the figures with the iron ones (...). The bronze tips are very finely cast, often iwth delicate very thin wings, while the iron tips are much simpler castings. The technical considerations involved in the development of the crossbow are too complex to consider here, but it is clear that aerodynamic factors play a crucial role in the true flight of a missile flying at crossbow speed. A precisely cast tip would be of great advantage, and bronze would naturally have been the metal of choice for any kind of precision casting. Whenever it was economically feasible, bronze would have been preferred for crossbow-bolt tips. Iron shafts gave a saving in cost without influencing quality; in situations in which economics demanded the use of iron for the tips as well, however, a consequence was a reduction in quality.
Also, the far greater mass of an iron crossbow bolt will GREATLY reduce it's velocity and effective range! (it's very easy to make excellent bolts out of bamboo) As with all things having to do with Chinese history you have to see it more as propaganda than history!
As to the HUGE numbers of Han crossbowmen, think of (first) it's much easier to teach an untrained peasant to fire in un-aimed Napoleonic volley fire, than teach them how to shoot a bow (why the Mongols won so easily)! and that being said try to imagine that (volley fire) from "thousands" of crossbowmen with the aforesaid iron bolts, it would be tons and tons of iron as a gift to the enemy who would only have to stand back out of range and return fire with bamboo bolts!
I guess that you've never tried to fire a crossbow, or make an axe/knife/bodkin out of anything, but the reason that iron took over the world was that it made better weapons and tools! Also, the far greater mass of an iron crossbow bolt will GREATLY reduce it's velocity and effective range! (it's very easy to make excellent bolts out of bamboo) As with all things having to do with Chinese history you have to see it more as propaganda than history!
As to the HUGE numbers of Han crossbowmen, think of (first) it's much easier to teach an untrained peasant to fire in un-aimed Napoleonic volley fire, than teach them how to shoot a bow (why the Mongols won so easily)! and that being said try to imagine that (volley fire) from "thousands" of crossbowmen with the aforesaid iron bolts, it would be tons and tons of iron as a gift to the enemy who would only have to stand back out of range and return fire with bamboo bolts!
And like what others had also mentioned... the Mongols didn't win easily... and even after they win, archery is not the only thing that allow them to win, please study a bit more before coming out with such generalise statement.
Back to the discussion about Alexander vs. Qin. I think it is reasonable to suppose Qin Empire was comparable to Roman Republic of the 2nd Punic War Era (almost contemporaenous with Qin) in population, economy and military potential. I think as a tactician Alexander was comparable to Hannibal, and the army Alexander took from Persia eastward is if anything significantly weaker than the army Hannibal commanded at battle of Cannae.
The Roman Republic with its Italian traditional and reliable vassal states at the time had a population of about 8-10 million. With the war waging potential this population provided Rome was able to absorbed multiple serious tactical defeat dealt by Hannibal in quick succession, including one diseaster where it lost 80K of its better troops in one battle, and then drag the war on for 15 years, opening multiple secondary fronts to sap the strength of Carthage and block hannible's route of supply and retreat. By refusing to come to battle with hannibal, but keeping an army always on Hannibal's tail and this depriving hannibal of forage everywhere he went, Rome ultimately trapped hannibal for 12 years in the toe of Italy, before eventually ultimately defeating Hannibal in Zama. I suspect if Alexander led his army into Qin territory, even if he was able to inflict some telling intitial tactical victories, he would still be worn down and ultimately defeated in much the same way.
If Alexander makes it to Qin, it would be one army against the war waging potential of a large populous, and disciplined state. If the state is not rash and try to stake all on one battle, then the state will eventually win no matter how good the army is.