The Chergui

Timeframe: October 1895-April 1896.
Belligerents: The Crown of All Spains vs. Mahdist insurgents.
Outcome: Pyrrhic Spanish victory

In 1893, Yusuf II was faced with a small nightmare: a military standards war. It took the better part of a year to sort it out, and no small investment of money and man-hours, before the Caliphal Army was uniformly issued matching rifles and ammunition that wouldn't explode. The Port-Royal musketoon had prevailed, and the army now faced a problem: what to do with all the noncompliant hardware?

Refitting it was too much trouble; they already had their hands full retooling sights, adjusting barrel lengths, and making similar conversions on thousands of already-assembled guns. Issuing them down the totem pole would force the very logistical nightmare they'd just spent 15 months sorting out. Issuing them to the navy might work, but would still be a logistical headache. (More importantly, the Army Secretary thought the Navy's adoption of .49-94 a decade prior a smashing political victory, one he had no desire to undo.) This being the UCNA, they'd already rechambered a number of obsolete guns for the rejected H11 cartridge - proofs of concept, substitute standards, all sorts of stuff.

The fateful solution was to sell the useless crap abroad.
And it attracted a modicum of interest. Naples [details?] considered adopting it before running into budget problems. A few hunters discovered that it was flat-shooting and effective on deer, and the better stuff was snatched up quickly.

Classed as hunting rifles, the cheaper guns managed to escape Spain's attention long enough to be discovered and bought up by rebels, who took an evening over drinks to figure out things you could do with a gun that shot faster, flatter, further, and harder than the colonial authorities'.

A brief outline of the Chergui

Spanish Morocco never had the best lines of communication. While they'd struggled with telegraph wires, lapses in communication were fairly common.

• The first concerted violence started in early October, on the Saharan side of the Atlas Range. Coincidentally, at the same time an unseasonably early dust storm kicked up; lapses in communications were chalked up to "the chergui" rather than to any Mahdist activity. By the time it became clear that there was Mahdist activity, the initial handwave had become its official name.
• By late October, the revolt had gone regional. Several tariqas [who?] had sworn their allegiance to the leaders [who?], and Spain was receiving the first reports of smokeless warfare with fairly long, heavy bullets: entire ranks pierced with single shots.
• The war in the Atlas: By this point, the Crown was panicking; the Moroccan colonial CIC [who?] was tasked with stopping the Mahdist advance to Fez el-Bali at any cost. His response was to cut the route between Fez and Sijilmasa with mountain artillery and send troops behind it. It worked, more or less...
• The Rif breakout: ...until the sirocco picked up again. The insurrection fell back, launching scattered attacks just long enough to tax the Spanish supply lines and goad them forward. Around Christmas, the order was given to withdraw back across the Atlas, but by that time enough forces had simply worked around the Atlas range to launch a credible run for the Rif itself.
• The Battle of Marrakech: The bloody turning point of the war is at Marrakech, where the Spanish forces are thrown into a city fight. It's a tactical victory for the Mahdists, and a massive strategic failure; even though they take the city, they've shot through almost all their "magic bullets" doing so. Once again - and for the first time in the entire uprising - the Spanish have the technical lead.
• Scorching the earth: On the defensive again, the Mahdist forces fall back across the Atlas. Pursuit is slow, methodical, and punishing; a number of ksars are systematically annihilated in the process. Most of the Chergui's leadership escapes, alive but neutered and out of ammunition, into the Saharan trade network.

The Chergui's aftermath

The Chergui came as a hell of a shock to the Crown of All Spains. Up to that point, Mahdist forces had usually been ill-equipped and, more importantly, comparably equipped; especially in the colonies, the Spaniards had no plans or preparations against an enemy that outgunned them. The Chergui collapsed only when it ran out of magic bullets.

Even worse, the Chergui was the first time Mahdists had ever received significant aid from the UCNA before. There was no comfort in Moorish apologies; if it was accidental, what would a deliberate Umayyad-Mahdist alliance be capable of doing? Spanish military doctrine has evolved accordingly.

• Spain's first action after the Chergui was to transition to smokeless. Their caliber? The UCNA's H13 smokeless cartridge, rim and all. Was this sucking up to Yusuf II, acknowledging the H13 to be damn good, or standardizing with the most likely enemy? Yes.
• Portugal, which hadn't been involved in the Chergui, saw this as a good reason to adopt a tested, battle-proven caliber. Their choice? The H11 ball that'd just bloodied the Maghrib, with the rim clipped off and a few other cosmetic changes made.

For the scattered insurgents, the Chergui was an enormous shakeup too.

• Prior to the Chergui, the Berbers (lacking firearms) had fallen from military prominence. Even if they were out of ammunition, they had guns - guns like the world had never seen before. They also had an appreciation for the limits of those guns (specifically, that they work best at long ranges); ever after, Saharan warfare has restricted smokeless guns to long-range use, reserving black-powder pieces for close quarter combat.
• It bears noting that these guns also needed ammunition, and a very specific kind of ammunition at that. It could be handmade, in a kludgy way, by swapping bullets between cases, but it wasn't too long before Seadling (and others) started loading fresh H11 cartridges. These bullets have become a trade good, prize commodity, and international currency recognized from the Sahel to the Sudan (where certain numbers of them are equal in worth to cows for the sake of bride prices.)