Would full plate armors continue to evolve and expand in use? Could they eventually get used by islamic powers in direct competition with europe like the ottomans? Would be the crossbow the one to keep evolving against this armors?
I mean gets exposed to Europeans later.Trick question: it gets discovered in China 300 years later than OTL but would be exposed to Europe at roughly the same time
Would full plate armors continue to evolve and expand in use? Could they eventually get used by islamic powers in direct competition with europe like the ottomans? Would be the crossbow the one to keep evolving against this armors?
This is tricky because plate reappears in Europe around the same time as gunpowder starts seeing use in warfare; they are linked by the technical capabilities of the continent, basically, and later on directly influence each other's developments.
But let's pretend that having powder is not necessary for the development of plate harness, and it appears completely independently, eventually looking like some late 14th c. setup.
So immediately notable is that the people wearing it technically wouldn't need any face tempering much less getting shot-proof as OTL. Even 15th c. steel will stop bows and all but the heaviest crossbows and that might be the "good enough" range for a god long while.
On the other hand if European metallurgy keeps developing parallel to OTL even without shot/powder (I'm not sure it will) and there's a push to make more complete protection, then I'd expect melee combat to be the main way battles are won long long long into the ATL equivalent of the early modern era.
No cannons means small castles still have inherent defensive value. Ship battles are fought primarily by boarding, No shot, and good plate is pretty much impervious to anything an average person can realistically use. Expect a lot of polaxes and designs that are primarily aimed at stopping those rather than deflecting kinetic energy from arrows/bolts and balls/shot, and harnesses that encumber the wearer as little as possible while he climbs ladders or fights on ships etc.
This all, while correct, assumes that everybody wears a full plate armor but AFAIK this was usually not the case with the foot soldiers who routinely had been wearing half-plate or even something less expensive.
Now, about the gunpowder-less developments, the Swiss (who usually were not wearing any armor to show their disdain to the enemies) were already there and quite effective against the knights in full plate armor so it was only a matter of time for the similar pikemen units being created (as in OTL) in Germany and Spain pushing the knights somewhat aside as the main military branch.
Of course, without a gunpowder the process is slower but the fact remains that the knights are pretty much powerless against these columns.
The front ranks of both Spanish and German infantry units were quite well-armoured (having the gear was an absolute requirement for both the position and the pay that went with it), and their captains typically were in cap a pie same as any Sir de Wherever with his polaxe would have been. I'd expect that to stay the same or even increase as armour became cheaper and cheaper. There's no Bicocca equivalent to convince anyone otherwise.
I'd just expect better-armoured gentlemen fighting on foot, predominantly, possibly with pikes as well, which was basically the case anyway (polaxes, halberds, cut-down lances, and later pikes were all widely used). At the very least increasing the proportion of armoured men in your pike column would avoid a repeat of something like Flodden or Lambert Simnel's disaster.
The pike vs. gendarme-on-horse balance is kind of a curious thing: the gendarmes can't really do anything to a pike square, but the pikemen aren't all that effective against anything but light infantry when it actually comes to overrunning positions. They can't catch horsemen who don't want to be caught, they can't force walls, they can't force a defended camp.
I'd expect that role to be fulfilled by some other kind of professional infantry, maybe crossbowmen or bowmen in the English style, or shield-men like the Spanish and so on had. And the pikemen would be needed to defend that infantry from other pikemen or from cavalry.
Most importantly though, without field cannons, wagenburgs would remain a major tactical trick and can be held by those same crossbowmen or archers. A lightly-armoured pikeman is just as worthless against a wagernburg as a gendarme, possibly more because he's more likely to be killed rather than survive long enough to retreat.
That light infantry can't act too far outside the pikemen protection and can't attack or chase the cavalry.
Not necessarily because they have not just the pikes but halberds and can move fast. Of course, wagenburgs of the Taborites worked good against the feudal militia but in the less organized cases they could be taken as happened to the Order's wagenburg at Grunwald: practically all German infantry was there plus even some English archers but it was taken by storm. Without the cannons, etc. "firepower" of wagenburg is quite limited.
You might still get mounted crossbowmen as an option for harassing foot, I guess (don't think it'd worl that well against contemporary horse), and there is some space left for traditional bowmen and crossbowmen, but English longbowmen aren't immune to being overrun by determined pikemen or indeed gendarmes unless they're really dug in (there are lots of examples where English-style infantry didn't manage to hold against pikemen, and a few examples to the contrary, mostly against Scots).
They could still be very useful dug in (as would be crossbows), which is why I suggested the wagenburg.
Hm possibly also true. I just don't want to give too boring of an answer, that's all. I'm sure actual historical people would be more creative than my suggestions are.
No cannons means small castles still have inherent defensive value.
Counterweight Trebuchets say 'Hi'
It predated cannons large enough to damage walls by several hundred years.
After all, Edward the First had plenty of luck with 'War Wolf' and the dozen or so others that he built, 40+ years ahead of Crecy, that fired stones far smaller than War Wolf's 300 pound projectiles. Cannons capable of firing 100 pound stones were rare even 30 years after that
Counterweight Trebuchets say 'Hi'
It predated cannons large enough to damage walls by several hundred years.
After all, Edward the First had plenty of luck with 'War Wolf' and the dozen or so others that he built, 40+ years ahead of Crecy, where 'gonnes' fired stones far smaller than War Wolf's 300 pound projectiles. Cannons capable of firing 100 pound stones were rare even 30 years after that