As queen regnant of Sicily, she reigned jointly with her spouse and later with her infant son, the future Holy Roman Emperor Frederick II.

Shortly after becoming empress, she was involved in the succession war against her illegitimate nephew King Tancred for the Sicilian throne, during which she was captured, though she was later released unharmed.

[1] Shortly before ascending the Sicilian throne, at the age of 40, she gave birth to her only child, Frederick, thus continuing the bloodlines of both the Holy Roman Empire and the Kingdom of Sicily.

Boccaccio related in his De mulieribus claris that a prediction that "her marriage would destroy Sicily" led to her confinement to remain celibate, and by the 15th century, the monastery of Santissimo Salvatore, Palermo, claimed Constance as a former member.

Historian Mary Taylor Simeti has suggested that Constance, a potential heir to the throne and a valuable pawn in international diplomacy, would not be lightly ceded.

[citation needed] In the spring of 1168, during the reign in Messina of her elder nephew King William II, opposition to the Chancellor, Stephen du Perche, grew intense.

Her betrothal to Henry, King of the Romans, was announced 29 Oct 1184 at the Augsburg episcopal palace,[4] an event that Pope Lucius III initiated rather than objected to.

Before leaving Sicily, William II had three important nobles (his cousin Tancred, Count of Lecce, Roger of Andria, and vice chancellor Matthew of Ajello) swear fealty to her as the probable successor to the throne at the curia of Troia.

Abulafia (1988) points out that William did not foresee the union of German and Sicilian crowns as a serious eventuality; his purpose was to consolidate an alliance with an erstwhile enemy of Norman power in Italy.

Knowing that Sicily's Norman aristocracy would not welcome a Hohenstaufen king, William made the nobles, and the important men of his court, promise to recognize Constance's succession if he died without direct heirs.

Constance then accompanied her husband at the head of a substantial imperial army to forcefully take the Sicilian throne from Tancred with the support of the loyal Pisan fleet.

Salerno, Roger II's mainland capital, sent word ahead that Henry was welcome and invited Constance to stay in her father's old palace to escape the summer heat, and take treatment from doctors for her infirm health.

At Naples, Henry met the first resistance of the whole campaign, and was held up well into the southern summer from May to August, by which time much of the army had succumbed to malaria and other diseases.

Once Henry had withdrawn with the bulk of the imperial army, the towns that had fallen to the Empire immediately declared their allegiance to Tancred, for the most part now fearing his retribution.

Constance presented herself on a balcony and spoke to them in the tone of mild remonstrance and admonition, trying to tell them that the situation might improve and the defeat of Henry might be exaggerated by Nicholas, but the Salernitans were determined to capture her for Tancred, so they continued the siege.

After a rapid negotiation with Elia di Gesualdo, a distant relative of Tancred, Constance voluntarily went out under the condition that her German guards were allowed to leave unharmed.

She was then arrested by Elia (and some barons of Apulia who were related to her) and delivered to Tancred in Messina by Admiral Margaritus of Brindisi (her brother-in-law who had helped in the defence of Naples), on a bireme galley or dromon with 200 rowers.

She was in her attire as empress, wearing a dress quilted with gold and decorated with roses, a cloak covered with precious jewels, and her hair was strewn with gems, making her look like a goddess.

Matthew wrote a letter to Tancred in her presence, suggesting he put Constance in the Castel dell'Ovo in Naples in the custody of nobleman Aligerno Cottone.

In addition, Matthew wrote to Aligerno, ordering "ut imperatricem in Castro Salvatoris ad mare bene custodiat" ("that he guard well the Empress in the Castle of the Savior by the sea", i.e., Castel dell'Ovo).

(The Pope hoped that by securing Constance's safe passage back to Rome Henry would be better disposed towards the papacy and Celestine would be able to keep the Empire and Sicily from uniting.)

They traveled through the Strait of Messina, but before they made it to Rome they met imperial soldiers and the pro-Hohenstaufen abbot Roffredo of Montecassino, and Constance asked them for help; they were able to intercept the convoy at Ceprano despite the opposition of the cardinals and escorted her safely across the Alps, ensuring that in the end neither the papacy nor Sicily scored any real advantage in having had the Empress in their custody at all,[10] only less than a month after her release; Within two weeks Henry and Constance reunited in the imperial castle of Trifels.

Later that year he moved south, leveled Salerno to the ground in revenge for arresting Constance, entered Palermo unopposed, deposed Tancred's young son William III (died 1198), and had himself crowned instead.

On 26 December, the day after Henry was crowned at Palermo, she gave birth to a son, named Constantine after herself (later renamed Frederick-Roger, i. e. the future Frederick II, Holy Roman Emperor and King of Sicily) in the small town of Iesi, near Ancona.

After Henry's death, initially she had upheld for her son the double title Romanorum et Sicilie Rex, but she abandoned the German claim after the coronation of Frederick in Palermo, May 1198.

[24] She surrounded herself with local advisors and excluded the ambitious Markward von Anweiler from a position of power, attempting to restrict him to his fief in Molise, as well as Walter of Palearia and Conrad I, Duke of Spoleto.

In 1215, Frederick had his father reburied in a porphyry sarcophagus taken from Cefalù (which was one of the two sarcophagi Roger II had commissioned for himself; according to the emperor's order, the other one was reserved for himself).

[26] Historian Vinicius Dreger writes that Constance was probably "maybe the most important woman of Western Europe in late twelfth century", yet "about her, as on most of her predecessors and contemporaries, we know little.

When permitted to be betrothed to Henry she continuously objected for that she thought her advancing age would become an obstacle, but in vain, "Thus did a wrinkled crone abandon the sacred cloister, discard her monastic veil, and, royally adorned, marry and emerge in public as empress".

Giovanni Villani said William I sought to put her to death due to the prediction until Tancred a bastard son of Roger I, Count of Sicily persuaded him to send her to a convent.