Suppose for a second that physics worked just ever so slightly differently, and gunpowder didn’t exist. Everything else still worked the same. Bombs, grenades, rockets, internal combustion. The only difference in this hypothetical world from our own is that the substance we call gunpowder can not be made.
Another caveat: in the absence of gunpowder, it’s entirely likely that something almost indistinguishable could be used. Maybe it’s slightly less efficient or more expensive than gunpowder, which is why it never took hold in our own reality. Regardless, when I say ‘no gunpowder,’ that’s my way saying ‘no guns.’
My initial thought was to try and find some way to have a modern setting where melee and swords were relevant alongside–and even superior in many cases to–ranged weaponry.
People are still going to want to be able to kill each other from across a room, and crossbows are fairly similar to guns. Here’s how I see crossbows evolving in a world where guns aren’t available.
First of all, they lose the whole bow part. Modern crossbows use springs to push the bolts. Top of the line models use titanium springs which are more durable and more powerful. ‘Civilian’ models use steel springs, still quite serviceable. Some crossbows have multiple arrays of springs and the trigger is created such that successive squeezes fire off different springs, allowing multiple shots without reloading/rearming.
The crossbows still have a crossbar, which pivots and usually remains in line with the bow, giving it a slim form factor. In combat, the bar is pivoted out and braced against the off-hand’s forearm. Even with the leverage, cocking the bow is difficult. Practiced shooters learn to use the recoil from the bow to help them rearm faster and more easily.
Modern materials make crossbows even more deadly and much more efficient, but still a far cry from firearms. Even the best of them are slow to rearm and reload, and doing such in a combat situation is largely feasible only when your enemies aren’t attempting to engage you in melee. And just for good measure, let’s pretend that a highly-skilled person can deflect crossbow bolts with a decent chance of success, at least turning for example a heart shot into a shoulder shot, if not outright knocking the bolt away.
Blade technology has been improved as well. Modern metallurgy makes blades more resistant to wear, sharper, and lighter.
Originally created for the soldiers, spring-loaded arm-blades displaces knives as the ‘concealable’ weapon of choice. Gang members hide the slim metal sheaths under baggy long-sleeved shirts. They’re quick and easy to deploy, nearly impossible to disarm, and the sword and arm mounting provide excellent defense against others’ melee weapons.
Non-lethal varieties are also available. Police, for example, are outfitted with baton versions of the arm-blades.
There’s also still a place for traditional, hand-held weapons. In particular, the arm-mounted weapons are designed to be worn regularly and are lightweight. You also lose hitting power by virtue of not being able to use your wrist to help bring the weapon around to strike. Hand-held swords and axes are thus more powerful and superior against armored targets. Hand-held weapons are also crafted to be somewhat flexible below the striking edge, adding a whip-like quality to them.
And so… that’s what I’ve got so far. A treatise on a modern world with swords and cellphones, bombs and bolts.