The Heroic Sacrifice of EAS Persephone at Tirrith. At the time Earth was neutral, and the Persephone found herself the only ship that could stop a Dilgar scouting force from slaughtering a group of escaping refugees. So the Persephone, who, having a jump engine, could have easily escaped, took on fifteen Dilgar ships and destroyed them all, allowing the refugees to reach the jumpgate and escape, but getting the jump engine wrecked in the process right when Jha'dur entire elite force showed up. So, what the Persephone did? She charged straight at the nearest dreadnought (that just happened to be Jha'dur's original flagship) to try and destroy that too. Between the Persephone defeating the scouting force (with help, but what ships Tirrith had was little more than target practice and the Earthforce cruiser had to do most of the job) and the final charge it was the first hint that the Dilgar had someone to fear, and it showed the League they had someone capable and willing to stop the Dilgar because it was the right thing to do.
Also, the escape of the soldiers from the Persephone who were on the planet when the Dilgar arrived. Not only they made the Dilgar soldiers run all over the planet (and Alfredo Garibaldi killed one of their elites with a crowbar), took back the Persephone's black box and stole important Dilgar data before escaping with a shuttle, but the escape vehicle's was Jha'dur's private shuttle. The Dilgar officers who allowed the latter ended helping Jha'dur's experiments.
The two battles of Markab are two moments of awesome for Earthforce.
The first had Earthforce bask in the glory of awesomeness. Everyone knew the Dilgar could be defeated and forced to retreat, but it costed men and ships, and there was no guarantee the Dilgar wouldn't just return with greater strength. That, and Jha'dur never lost or retreated, she only knew victory. This time Earthforce showed up... And the Dilgar led by Jha'dur ran. The Markab, who were in utter despair just a moment before, called it a miracle from the gods.
The second had Jha'dur return with every ship on that front (by large and far the finest ships of their entire military with the exception of the Home Fleet) to try and break Earthforce. By the end of the battle the Dilgar were routed, most of their finest ships had been destroyed either by the Nova-class dreadnoughts or by an insane number ofnuclear weapons, and Jha'dur had been nearly killed twice and was comatose.
This and other exploits of the Nemesis culminated in a moment of awesomeness in the final chapter. The crew of the SpaceRace was complaining that they should lead the victory parade when Jennifer mentioned the leading ship was the Nemesis, shutting up all protests.
Earthforce had sent a fleet through Narn space to reach the Drazi and help on their front, but had to stop at the border to acquire the new beacon. The local Narn commander was threatening to attack if the Earthforce fleet did not surrender... Cue G'kar showing up and browbeating the commander into submission while pointing out that Earthforce had been authorized to pass and he would have known had he read his orders. The poor bastard was already feeling doomed before the Earthforce commander pointed out he had had dealing with the Dilgar, by then hated by the Narn due what Jha'dur had done on Hilak.
Stro'kath forced the retreat of the Dilgar Third Strike and the Home Fleet while almost out of fuel and ammunitions. How? Easy: Fleet-wide ramming attack. Even better, had the Dilgar not retreated the losses in veterans, ships and one very capable admiral would have been crippling and left the way to Omelos open. Either way, he would have won. And he was improvising.
Pretty much every time Stro'kath is in battle. His crowning achievement is his crippling the Dilgar war machine and defeat of Jha'dur, without ever facing her, by simply attacking the staging area where the Dilgar were keeping a large part of their merchant navy to refuel the incoming Jha'dur and ignoring the warship escort to annihilate the cargoes, before leaving. When Jha'dur finally showed up, she was forced to concede her part on the Drazi front was finished, and in the later stages of the war the Dilgar suffered heavily for their inability to refuel and rearm their warships.
Londo and his friend Urza Jaddo took part to this battle as fighter pilots, and were in fact the ones who baited the Narn into attacking the Centauri fleet. They not only got away with it without a scratch, but also made a few kills.