My favorite example comes from the American Civil War. On 13 December 1862, the Federal Army of the Potomac attempted an assault crossing of the Rappahannock River at Fredericksburg, VA, in the teeth of defenses manned by the Confederate Army of Northern Virginia, partially entrenched on high ground south of the town. Although the Federals improbably managed to cross the river and cut through Fredericksburg itself, several attacks on the high ground at Marye's Heights failed with extremely lopsided casualties. At certain points on the Confederate front line, rebel infantry massed behind stone walls eight deep, with seven men loading rifles to pass up to the man at the front, who would blaze away continuously at the Federal columns.
Seven months later, on 3 July 1863, the Army of the Potomac faced off against the Army of Northern Virginia once again, except that this time, the Federals were defending behind a wall and the rebels were making an attack against heights across open ground. In the climactic moment of the Battle of Gettysburg, over ten thousand rebel infantry assaulted Federal troops on Cemetery Ridge. The similarity of the situation was not lost on the bluecoats, who picked off the rebel infantry from behind split-rail fences and walls while crying, "Fredericksburg! Fredericksburg!" Just as the Federal attack on Marye's Heights was turned back, so was the Confederate attack on Cemetery Ridge - a point in the battle often referred to as the high-water mark for the entire rebellion.
There's another neat one from a few decades earlier. One of the most useful elements of Napoléon I's
Grande Armée was an exceptional cavalry superiority. French cavalry was generally more numerous, more experienced, and better-led than its opponents. In 1805, the French cavalry played the crucial role in the surrender of Mack's army at Ulm; in 1806, following the twin victories at Jena and Auerstädt, Joachim Murat's horse seemed to be everywhere at once, compelling the surrender of nearly every fortress in Prussia, seizing Berlin, and turning the Prussian retreat into a total rout.
But in 1812, Napoléon's horse and horsemen died in Russia. As the Emperor scrambled to rebuild his shattered forces in 1813, he did an excellent job of rapidly assembling large bodies of infantry and artillery with enough skill to go toe-to-toe with the Allied regulars. But there simply were not enough horses and horsemen to mass large numbers of cavalry. In the spring campaign of 1813, Napoléon won victories at Großgörschen and Bautzen, although they were less tactically decisive than many of his previous battles. More importantly, the Allies were able to retreat in good order and protect their marching columns because of their immense superiority in skilled cavalry. Clouds of Cossacks and
Streifkorps interfered with French communications and supplies, while the heavy units achieved a surprise victory by ambushing a pursuing French column at Haynau. Had Napoléon possessed his old cavalry, he probably would not have had to settle for the summer armistice that Austria negotiated in June, July, and August.
When the campaign resumed in late August, Austria had gone from neutrality to open hostility, but both sides were on a more or less even footing; Napoléon had somewhat fewer men, but possessed the advantage of interior lines. He still had not managed to build up his cavalry, though, and although the Allies took time to work out all the kinks in their integration of cavalry units, their superiority eventually began to tell. And, like the master had done ten years before, the Allied generals were able to unleash their cavalry against retreating French armies and convert victories into routs. Blücher's Army of Silesia did this to Macdonald's French Army of the Bober in the wake of the victory on the Katzbach on 23 August. But, more importantly, in the wake of the Allied victory in the apocalyptic Battle of the Nations at Leipzig from 16 to 19 October, what had been a relatively evenly matched affair turned into a French disaster. French errors trapped thousands of retreating troops, and Allied cavalry hounded the wreck of Napoléon's army across Germany. Once the Emperor had reached the safety of France, he had to create a fresh army once again to fight his war.
Rome deploying war elephants to great effect at Cynoscephalae is an example, given the bludgeoning Pyrrus's elephants gave the Republic in the prior century (I thought I read once that Rome used elephants during the destruction of Carthage, but I can't find sources to confirm that - that would be another great example if true).
I guess, except the Romans fought the Makedonians at Kynoskephalai, not the Epeirots. Kind of not the same thing.
But. If we're relaxing the criteria a bit, then surely the Prussian army would fit the bill.
In 1866, the new-model Prussian army fought a seven weeks' Brothers' War with Austria, culminating in the Battle of Königgrätz on 3 July. Austrian tactical doctrine emphasized the bayonet charge, delivered with speed and mass, as the decisive element in the attack; marksmanship was correspondingly deemphasized. Prussia, on the other hand, had supplied its infantry with the Dreyse model 1842 needle gun, the first widely-available breech-loading rifle in the world. With needle guns, the Prussians could reload incredibly quickly compared to virtually anyone else, allowing them to lay down a withering amount of fire. Twice during the battle, in the Swiepwald and again at Chlum, Austrian shock attacks were utterly smashed by smaller forces of Prussians armed with needle guns. The Dreyse rifle might be the best, and maybe only, example of a truly war-winning weapon: at Königgrätz, it proved to be the most important distinguishing factor between Prussian victory and a possible Prussian defeat.
In 1870, Prussia went to war once again. Its infantry were still armed with the needle gun, but their opponents had upgraded. Instead of Austrian shock charges, the Prussians had to contend with veteran French infantry, armed with the
chassepot, a breech-loading rifle that outperformed the needle gun in virtually every way, especially range. The Prussians could not duke it out with the French at medium range; French infantry could badly punish the Prussians without the Prussians being able to respond in kind. Furthermore, the circumstances of military operations meant that the Prussians were on the offensive all throughout the decisive opening phase of the war.
What resulted was a fairly gruesome reversal of 1866. Forced to resort to short-range firepower and shock to overcome the enemy, Prussian columns took horrifying losses in battles against the imperials at Spicheren, Vionville-Mars-la-Tour, and Gravelotte-St. Privat. Prussian casualties outnumbered French in all of these early battles. In particular, the infamous assault of the Prussian Guard on St. Privat on 18 August was a total disaster: a head-down charge over open ground that was cut to pieces long before it reached the French lines at a cost of thousands of dead and wounded. Unlike the Austrians, however, the Prussian butcher's bill had a purpose. The Germans took horrifying losses but in each battle, managed to envelop their French foes with superior numbers or at the very least compelled them to withdraw. German numbers, and German operational and strategic generalship weighted the scales on the one side; French command incompetence weighted them on the other. Gravelotte was a disaster, but it resulted in the main French field army withdrawing into the fortifications of Metz to be besieged and, ultimately, to surrender. After August, the Prussians were able to refine their technique and embrace greater coordination with their excellent artillery, to which the French had no answer; later in the war, it was French troops that would be launching the headlong attacks, and the Prussians who would cut them down on the defensive.
If memory serves, the Romans didn't user elephants against Carthage, but
Scipio Africanus neutralized the Carthaginian elephants at Zama with (IIRC)
trumpets.
More importantly, the Romans had convinced the Massylim, Qarthadast's strongest Numidian ally, to switch sides. Massylian cavalry fought for Rome at Zama, and helped deliver the decisive blow to Hannibal's infantry in the battle's final act. That's probably a much better role-reversal than elephants, which were militarily suspect in many classical battles.
