Louis the Lionhearted and the Sicilian ambition
Constance was not betrothed until she was thirty, which later gave rise to stories that she had become a nun and required papal dispensation to marry. The betrothal was announced 29 Oct 1184 at Palermo and she married Louis of France on 1186, Constance gave birth to a son named Henry on 1187 and later a son named Louis followed on 1189
The death of her younger nephew Henry of Capua in 1172 made Constance heiress presumptive to the Sicilian crown,after her elder nephew King William II, who did not marry until 1177, and whose marriage remained childless.
Nor would the kingdom's Norman nobles welcome a Capetian king. William made his nobles and the important men of his court promise to recognize Constance's succession if he died without direct heirs. But after his unexpected death in 1189, his cousin (and Constance's nephew) Tancred seized the throne. Tancred was illegitimate, but he had the support of most of the great men of the kingdom.
Constance accompanied her husband at the head of a substantial imperial army to forcefully take the throne from Tancred. The northern towns of the kingdom opened their gates to Lous, including the earliest Norman strongholds Capua and Aversa. Salerno, Roger II's mainland capital, sent word ahead that Louis was welcome, and invited Constance to stay in her father's old palace to escape the summer heat. Naples was the first time that Louis met resistance on the whole campaign, holding well into the southern summer, by which time much of the army had succumbed to malaria and disease and the imperial army was forced to withdraw from the kingdom altogether. Constance remained in Salerno with a small garrison, as a sign that Louis would soon return.
Once Louis had withdrawn with the bulk of the imperial army, the towns that had supposedly fallen to the French troops immediately declared their allegiance to Tancred, for the most part now fearing his retribution. The populace of Salerno saw an opportunity to win some favour with Tancred, and delivered Constance to him in Messina, an important prize given that Henry had every intention of returning. However, Tancred was willing to give up his negotiation advantage, that is, the Empress, in return for Pope Celestine III legitimizing him as King of Sicily. In turn, the Pope was hoping that by securing Constance's safe passage back to Rome, Louis would be better disposed towards the papacy and he was still hoping to keep the Empire and the Kingdom from uniting. However, french soldiers were able to intervene before Constance made it to Rome, and they returned her safely to France, ensuring that in the end, both the papacy and the kingdom failed to score any real advantage in having the Constance in their custody.
Louis was already preparing to invade Sicily a second time when Tancred died in 1194. Later that year he moved south, entered Palermo unopposed, deposed Tancred's young son William III, and had himself crowned instead.