Ogier was never more than a boy during his reign. He came to power at the age of five months, his great-grandmother, Judith, serving in his stead. He died at the age of 17, just barely over a year after reaching the age of majority.
The decade and a half of his reign was one of constant warfare, as Irish reactions to generations of Breton rule gave way to a series of crises on the island, pulling in England and Wales in full-fledged warfare. The teenaged king died having never known a moment of peace in his short life.
Judith, finding herself Regent of Brittany for an astonishing fourth time, saw to it that war with Ulster was a top priority scarcely after her grandson, Briant II's, body had cooled. It was, as she wrote at the time, a question of restoring the kingdom's priorities. The Duchy of Ulster, recall, had been let go of in the face of too much opposition from Wales and Munster. Judith aimed to rectify this mistake.
So it was that Breton troops found themselves embroiled in Irish warfare once again. In 1196, a large contingent of Breton troops, mainly footmen and archers, made the march from Leinster to Ulster, laying siege to Tyrone's cities as a top priority. The Ulster armies were outnumbered and outmatched.
Salvation for Ulster would come in the form of another rebellion by the restive Connacht. Duke Art I, the famed Imag's son and heir, died in May of 1196, shortly after the invasion of Ulster began. His son was an ambitious and tenacious man named Finnsnechtae. The day that Art was buried, his son declared a perpetual rebellion against Brittany in support of Ulster and all Irishmen everywhere.
So it was that the holder of the ducal seat of Connacht, for the third successive generation, rebelled against the crown of Brittany.
The three way war raged for two years before Wales, sensing another chance to sneak the county of Breifne away, invaded the Irish coast with a force matching the size of Brittany's initial invasion force. 1198 was a year of stalemate. The Ulster and Connacht forces had largely been crushed by Brittany, but neither Wales or Brittany could get the better of the other. It was a replay of the Irish wars of Briant II's reign, with Wales outmatched on a man per man basis but Brittany unable to bring the full might of her arms to bear due to distance.
In 1199, Queen Mother Judith, Regent of Brittany, great-grandmother to King Ogier, grandmother to Briant II, mother to Barthelemi I, wife to Briant I, died in her sleep of old age. She was 79 years old.
It is impossible to overstate the importance of Judith in the history of Brittany. Of the combined 41 years on the throne of her grandson and great-grandson, she was regent for 24 of them. She was spymaster for all of them, and her son's and husband's reigns, as well. She was a force of nature, energetic and vital to the last. She did terrible things, for certain, but given the short, periodically weak reigns of her descendants, such things were perhaps necessary to keep the kingdom together at all. As well, viewed in total, her crimes (excepting the murder of her first great-grandson in his crib, which is fairly singular in its monstrosity, at least in the region) are no worse than those of most contemporary male rulers.
With Judith's passing, Chancellor Odo de Rohan became Regent of Brittany. He was more personally diplomatic and outgoing than Judith, though without the knack for grand strategy. The prolonged stalemate in Ireland may be lain partially at his feet, as he dithered more than once when swift action was required.
The boy king suffered another personal blow when his mother, Queen-Mother Barbara, married the Holy Roman Emperor, Kaiser Berthold von Rheinfelden. This was to unite the houses of Salian and von Rheinfelden in marriage. Berthold was, at the time, rather insecure in his throne. Ogier, who was emotionally fragile and a bit slow, was left bereft of family besides Marguerite, his older sister.
The war raged on with no end in sight. Indeed, it actually broadened. Chancellor Odo made a terrible mistake in 1203, when Prince Idwal of Wales was captured during the Battle of Cavan. He was the youngest son of the Welsh king. Annoyed at Welsh intransigence, Odo ordered the 19 year old prince executed, rather than ransomed. His hope was that it would ruin Welsh morale; the opposite occurred. The Welsh doubled down and never forgot what they perceived as a terrible crime on the part of the Bretons.
1207 brought further expansion of the wars. On the home front, both distant Angouleme and Cornwall rebelled. In Ireland, the English laid claim to Ulster, bringing them into the abattoir. It was now a five way conflict on the Emerald Isle. Connacht was nearly spent, Wales on the ropes, Brittany close to declaring victory, but the arrival of the English changed the calculus entirely.
The next year, Aquitaine attempted to reclaim Angouleme whilst Breton attentions were turned northward. The historically French province was all but abandoned to the Aquitainians, as what few troops could be spared from the conflict on Ireland were sent to Cornwall.
Connacht finally, reluctantly, surrendered in 1208. Finnesnachtae was thrown in prison, his ducal title stripped in favor of his five year old son, a boy who, it was hoped, would prove pliable. The former duke was never released from captivity; he died three years later.
There was still no room to breathe. While the 12 year Connacht rebellion had finally been put down, fighting with Ulster wore on. The English were somewhat distracted by a conflict with France over the rule of Anjou, but it was temporary. In 1208, even Odo knew that fast action was needed to secure the Duchy of Ulster, before the superior English armies had time to turn their attentions back to Brittany.
Abroad, February of 1209 brought the unsuccessful conclusion of the Third Crusade. What had been promising in the years when Briant II had set off on crusade had turned to ashes for the crusaders, just as the prior two crusades had. The Islamic states of the Levant were simply more cohesive and stronger than anything Christendom could muster. Especially hard hit was Denmark, who had squandered enormous amounts of treasure and blood to prop up the crusade. After 21 years, the kingdoms of Europe had nothing to show for all their efforts but a generation of dead men.
Wales would, in 1210, prove meddlesome to Brittany's war efforts, this time in Cornwall. The Welsh invaded in the hopes of claiming the Cornish peninsula but were driven back handily, though the Bretons were forced to rely on mercenaries to bolster their forces. In April of 2011, Cornwall would surrender, the title being given to long dead Duke Eon's brother, Drogon.
Ogier took the throne in truth as well as name on July 24, 2011. He was, as a young adult, a kind, brave young man. He also kept up the de Rennes tradition of budgetary skill. Interestingly, accounts by his sister and friends described him as being quite a bit slow, though his knack for numbers (often done personally, in his own hand, over the objections of his steward) contradicts this. Some historians have theorized that he may have been autistic, with the attribution of dim-wittedness being a mistaken product of its time.
Two months after his coronation, Ulster finally rejoined Brittany. This did not, however, mean the end of the war. England still had her sights set on claiming the duchy and, with the loss of Anjou to the French in 1210, had no distractions. With Ulster pledging to Ogier, the English were driven back, though all in Brittany knew it was temporary.
Brittany had been at war dating back to the beginning of Judith's regency in 1196. 1212 saw the possibility of peace, with the number of enemies whittled down to one, though that one (England) was the stiffest of all foes. 16 years of war had taken their toll on the people of Brittany's morale, both noble and commoner alike. That slim possibility evaporated in June of 1212.
Inexplicably, Sultan Mundir the Fat of Muslim Andalusia declared a holy war for Brittany. It was unprecedented. The Muslim states were usually the defenders in conflicts of the time. For a sultan in faraway southern Iberia to strike at the heart of western Europe was so bold as to be rash.
France rushed to Brittany's aid, with King Gaucelin II pledging his personal support and to ride side by side with Ogier against the sultan's forces. Ogier was said to have been surprised by this gesture but pleased. Never before in Breton history had the prospect of contact with the French raised their morale.
Ogier would never see battle against the Iberian Muslims. He had been wounded in a hunting accident after his wedding party. It had festered and turned gangrenous. He died on July 27, 1212 at the age of 17. Marguerite, his older sister, took the throne facing the English and the Andalusians in open war.