Indomitus Crusade
When the Primarch Roboute Guilliman declared the Indomitus Crusade the galaxy was quick to answer, numerous Chapter Masters offered their aid and the Smoke Jaguars were determined to be among them. Shortly after the liberation of Baal, when the Crusade was sweeping into the wider galaxy, Shade-Lord K'inich Yux sent emissaries to approach the Lord Commander and offer the services of his Astartes. Roboute Guilliman was somewhat off put by their exotic demeanour but they were hardly less strange than the Black Dragons or Iron Snakes, so they were accepted into the hosts.
The Primarch's genius immediately saw the potential of the Smoke Jaguars for the Lord Commander had need of many types of warriors, the lessons of the Great Crusade had taught him well that there were many forms of battle and he needed men of varied character to meet them. Thus the Smoke Jaguars were assigned to be the outriders of the Crusade, ranging far ahead of the Unnumbered Sons, alone and unsupported to harass and disrupt the enemies of Man until the bulk of the Crusade could obliterate them. To aid them Roboute Guilliman gave the Chapter a gift of Primaris Marines which they embraced enthusiastically; in particular they found great use for the Intercessors, Hellblasters and Rievers which soon became a staple of their campaigns.
The Primarch had already secured the services of the Raven Guard for covert operations, yet their galactic fame made them unsuitable for certain types of operations whereas the Smoke-Jaguar's anonymity worked in their favour.
Roboute Guilliman would use the Chapter as a harassment and distraction unit, oft having them attack an enemy from one direction to draw off forces only for the mass of the Indomitus Crusade to advance from another direction entirely. Another mission the Smoke Jaguars excelled at was commerce raiding, nipping at an alien empire's shipping and infrastructure, keeping them busy chasing ghosts and mist instead of attacking the Imperium.
Roboute Guilliman also saw another use for the Chapter by having them conduct field tests of some of Belisarius Cawl's more controversial and radical inventions, without the knowledge or sanction of Mars it must be noted. The Chapter pioneered the use of Grav-Chutes and grapple-guns for the Rievers, field tested unusually configured gunships that went on to become the Overlord pattern and they conducted live combat trials of Bolt rifle variants, Plasma weapons and more esoteric devices.
Many of these went on to be issued to the Unnumbered Sons, while others were quietly buried, redacted from all records and their very existence strenuously denied when emissaries of Mars made enquires. Sometimes Guilliman would even send the Chapter out into the galaxy to secure mysterious artefacts and devices which would then be turned over to Belisarius Cawl for further investigation or occasionally be sequestered by the Primarch himself for undisclosed purposes.
Thus, in a small and unremarked way the Smoke Jaguars played a vital role in the Indomitus Crusade, fighting unobserved and expecting no thanks yet knowing that their deeds were of immense value to the Lord Commander himself. In particular they took great pride that their tradition of appointing War-Leaders inspired Guilliman to create the position of Lieutenants amongst the Astartes, though it must be stressed that this honour is also claimed by three score other Chapters so here the Smoke Jaguars may be giving themselves more credit than is actually due.
