The matters at hand
It is the late spring of 1086. I, Duke Brian II of Munster, am faced with two traitors who would seek to keep my realm divided.
The first is Duchess Der-Lugdach of Connacht. My hope was that when she married my younger half-brother, Amalgaid, the two of them would bend their knees to my rule peacefully. Not so, as Der-Lugdach defied me, and Amalgaid sided with his wife over his blood. Not cool, bro. The armies of Munster crushed the Connachtian rebellion, and were set to take their fortress of Dromahair, when...
Lord Mayor Skofte of Ormond, my most powerful vassal, declared Ormond independent from my realm and raised his armies to oppose me. A descendent of Norwegian vikings that settled Ireland generations ago, Skofte made a reluctant friendship with my father, Duke Murchad I. Upon his death, that friendship was gone, and Skofte has made his distaste with my rule known ever since. In light of the Ormondian threat, my men were forced to abandon the siege at Dromahair and rush away south to meet Skofte. The Lord Mayor is known to be a genius, and thus will make a formidable opponent.
April 26, 1086: Duke Brian's 730 men meet Skofte at the Battle of Cashel. The rebels are routed, but manage to fell over 100 loyal Munsterians in the process.
May 13, 1086: Duke Brian meets with his son, heir, and marshal, Murchad, as their armies march to retake Ormond. Murchad desires lands of his own to govern, and Duke Brian promises to make him the new Lord Mayor once Ormond is back in loyal hands.
June 1, 1086: After the last of Skofte's forces are cut down at the Battle of Killaloe, the siege of Waterford begins. Duke Brian remembers hearing tales of how it almost fell to a paltry force of rebels during his father's reign - it is a poorly-built fortification, no true castle. It is high summer, food is plentiful, and all the roads are open. All in the Munsterian camps seem to agree that it will not hold for long.
August 13, 1086: Waterford is taken by the Munsterians. The 600 remaining men of Duke Brian's army turn once again north to finish what they started, taking Castle Dromahair and ending Der-Lugdach's defiance.
Just for occupying Ormond, my warscore will go up over time, and thus, the chances that Skofte will surrender. Now I just need to do the same in Breifne and my realm will not only be restored, but larger than it ever was before.
September 12, 1086: Brian defeats what few troops Der-Lugdach scraped together while the Duke was busy with Skofte, and the siege of Dromahair is reestablished.
September 14, 1086: Word arrives in the siege camps that the crafty Skofte has rounded up half a hundred brigands from the Ormondian countryside, and they look to recapture Waterford. Brian turns his forces to march all the damn way back there and deal with it.
Easy to take, easy to lose. Ormond is a wealthy and strategically important county, but it doesn't have a decent fortification to withstand a siege. And at the moment, I don't have the whopping 700 gold needed to build a castle there. Even with his relatively small force, Skofte will take it back before I capture Dromahair. I have no choice but to turn back around. After this, I'll be surprised if Skofte can pull together a decent force ever again.