So the Cretan War between the Ottomans and Venice that lead to the eventual Turkish conquest of Crete was born out of an act of Piracy against the Ottomans by the Knights Hospitaller. The Knights attacked an Ottoman convoy heading to Alexandria which was carrying pilgrims to Mecca including the Sultan's chief Eunuch. The Maltese briefly put ashore on nearby Crete to offload some sailors and horses and take on water. This was the casus belli as the Turks believed the Venetians were aiding the Knights. The Venetians protested their innocence and even executed the local garrison commander in Crete for dereliction of duty for not intercepting the Knights but to no avail. So suppose for whatever reason the Knights do not put ashore in Crete and instead manage to sail directly for Malta.
The Sultan was apparently bent on war and there was a concern among the Ambassadors in Constantinople that it could be against any one of them (the Austrians were engaged in attempts to renew their truce and were particularly worried about a new Turkish campaign in Hungary). So without a casus belli for war against Venice what if the Ottoman fleet sailed for Malta rather than Crete in 1645? How would a new siege of Malta proceed? On the one hand Malta is much more heavily fortified than it was in 1565 with the construction of Valetta on the high ground of the Sciberras peninsula. On the other hand the previous siege ended when relief arrived from Sicily. But in 1645 Spain is at a low point, at war with France and short of men and money so no aid is likely coming from that quarter. All of Europe is in fact at war at the time. Savoy and Modena are allied with France and at war with Spanish forces in Lombardy. The War of the Castro between the Papacy and Tuscany and Parma only ended in 1644. Innocent X had only just been elected the new Pope and was in conflict with the family of his Barberini predecessor. The Thirty Years War is still raging in the north tying down all the forces of Austria and the German states. And Venice is not going to get involved as the Serenissima will want to preserve its delicate relations with the Porte.
So without the prospect of aid could Malta hold out? Valetta is an impressive city but the outer Floriana lines are still under construction, though the Knights held out with less 80 years earlier. The Knights would also lack Venice's ability to blockade the Dardanelles but its debatable how effective that was during the Cretan War. On the other hand could a Turkish siege of Valetta be maintained as long as their OTL siege of Candia? Would the prospect of Malta falling to the Turks inspire any of the warring parities in Europe to end their conflicts and come to the Knights aid? The Papacy pushed hard OTL to end the Thirty Years War so Christendom could concentrate on fighting the Turks and defending Crete but it still took years before the War ended. So would Malta inspire any greater efforts here?
The Sultan was apparently bent on war and there was a concern among the Ambassadors in Constantinople that it could be against any one of them (the Austrians were engaged in attempts to renew their truce and were particularly worried about a new Turkish campaign in Hungary). So without a casus belli for war against Venice what if the Ottoman fleet sailed for Malta rather than Crete in 1645? How would a new siege of Malta proceed? On the one hand Malta is much more heavily fortified than it was in 1565 with the construction of Valetta on the high ground of the Sciberras peninsula. On the other hand the previous siege ended when relief arrived from Sicily. But in 1645 Spain is at a low point, at war with France and short of men and money so no aid is likely coming from that quarter. All of Europe is in fact at war at the time. Savoy and Modena are allied with France and at war with Spanish forces in Lombardy. The War of the Castro between the Papacy and Tuscany and Parma only ended in 1644. Innocent X had only just been elected the new Pope and was in conflict with the family of his Barberini predecessor. The Thirty Years War is still raging in the north tying down all the forces of Austria and the German states. And Venice is not going to get involved as the Serenissima will want to preserve its delicate relations with the Porte.
So without the prospect of aid could Malta hold out? Valetta is an impressive city but the outer Floriana lines are still under construction, though the Knights held out with less 80 years earlier. The Knights would also lack Venice's ability to blockade the Dardanelles but its debatable how effective that was during the Cretan War. On the other hand could a Turkish siege of Valetta be maintained as long as their OTL siege of Candia? Would the prospect of Malta falling to the Turks inspire any of the warring parities in Europe to end their conflicts and come to the Knights aid? The Papacy pushed hard OTL to end the Thirty Years War so Christendom could concentrate on fighting the Turks and defending Crete but it still took years before the War ended. So would Malta inspire any greater efforts here?