Siege of Tripoli (1551) in the context of "Murad Agha"

Hospitaller Malta, known in Maltese history as the Knights' Period (Maltese: Żmien il-Kavallieri, lit. 'Time of the Knights'), was a de facto state which existed between 1530 and 1798 when the Mediterranean islands of Malta and Gozo were ruled by the Order of St. John of Jerusalem. It was formally a vassal state of the Kingdom of Sicily, and it came into being when Emperor Charles V granted the islands as well as the city of Tripoli in modern Libya to the Order, following the latter's loss of Rhodes in 1522. Hospitaller Tripoli was lost to the Ottoman Empire in 1551, but an Ottoman attempt to take Malta in 1565 failed.

Following the 1565 siege, the Order decided to settle permanently in Malta and began to construct a new capital city, Valletta. For the next two centuries, Malta went through a Golden Age, characterized by a flourishing of the arts, architecture, and an overall improvement in Maltese society. In the mid-17th century, the Order was the de jure proprietor over some islands in the Caribbean, making it the smallest state to colonize the Americas.

Tripoli, today the capital city of Libya, was ruled by the Knights Hospitaller between 1530 and 1551. The city had been under Spanish rule for two decades before it was granted as a fief to the Hospitallers in 1530 along with the islands of Malta and Gozo. The Hospitallers found it difficult to control both the city and the islands, and at times they proposed to either move their headquarters to Tripoli or to abandon and raze the city. Hospitaller rule over Tripoli ended in 1551 when the city was captured by the Ottoman Empire following a siege.

The invasion of Gozo, also known as the siege of Gozo (Maltese: L-Assedju t'Għawdex), was an Ottoman invasion of the island of Gozo, then part of Hospitaller Malta, in July 1551. The attack, which was led by Sinan Pasha, Dragut, Kambil Bey and Salah Rais, appears to have been launched in retaliation for the capture of Mahdia by the Spanish and Hospitallers the previous year.

The Ottoman force briefly attacked Sicily before landing on the main island of Malta on 18 July, where the city of Mdina was briefly besieged and some villages were plundered. They then abandoned Malta and landed on nearby Gozo, where the Castello was bombarded for two days before its garrison capitulated on 26 July. The fortress was sacked and between 5,000 and 7,000 people – the majority of the island's population – were enslaved and taken to North Africa or Constantinople. The same Ottoman force went on to capture Tripoli from the Hospitallers on 14 August 1551.

Gaspar de Vallier was a Marshall of the Knights of Malta, who was in command of the fortress of Tripoli during the Siege of Tripoli (1551). He was French, from the region of Auvergne ("Langue d'Auvergne"). In Tripoli, he commanded 30 knights and 630 Calabrian and Sicilian mercenaries. The city was captured on 15 August 1551.

Upon his return to Malta, Gaspar de Vallier was heavily criticized by the Grand Master de Homedes, brought in front of a tribunal, and stripped from the habit and cross of the Order.