The Liber Secretorum Fidelium Crucis (literally "Book of the Secrets of the Faithful of the Cross") is a Latin work by Marino Sanuto the Elder. It is one of the "recovery of the Holy Land" treatises intended to inspire a revival of the Crusades. It has also been named as Historia Hierosolymitana and Liber de expeditione Terrae Sanctae, and Opus Terrae Sanctae, the last being perhaps the proper title of the whole treatise as completed in three parts or "books".
It was begun in March 1306, and finished (in its earliest form) in January 1307, when it was offered to Pope Clement V as a manual for true Crusaders who desired the reconquest of the Holy Land. To this original Liber Secretorum Sanuto added largely; two other "books" were composed between December 1312 and September 1321, when the entire work was presented by the author to Pope John XXII, together with a map of the world, a map of Palestine, a chart of the Mediterranean, Black Sea and west European coasts, and plans of Jerusalem, Antioch and Acre. A copy was also offered to the king of France, to whom Sanuto desired to commit the military and political leadership of the new crusade.
This work has much to say of trade and trade-routes as well as of political and other history; and through its accompanying maps and plans it occupies an important place in the development of cartography.
Proposals
The crusading plans of the Secreta are double: first, Egypt and the Muslim world on the side towards Europe (Syria, Asia Minor, the Barbary States (North Africa), Granada, etc.) are to be ruined by the absolute stoppage of all Christian trade with the same. By such an interdict Sanuto hopes that Egypt, dependent on its European and other imports of metals, provisions, weapons, timber, pitch and slaves, would be fatally weakened, and the way thus prepared for the second part of the campaign the armed attack of the crusading fleet and army on the Nile delta. With the aid of the Mongol Tatars of Asia, natural allies of western Christendom, and of the Nubian Christian kingdom of Makuria, the conquest of the Delta and of all Egypt was to be followed by that of Palestine, invaded and held from Egypt. Sanuto deprecates any other route for the crusade, and unfolds his plan of campaign, his bases of supply, his sources for the supply of good seamen, with great detail. Not only Mediterranean seaports, but the lakes of North Italy and central Europe, and the Hanseatic ports, are enumerated as nurseries of crusading mariners and marine skill. Finally, after the conquest of Egypt, Marino designs the establishment of a Christian fleet in the Indian Ocean to dominate and subjugate its coasts and islands. He also gives a sketch of the trade-routes crossing Persia and Egypt, as well as of the course of Indian trade from Coromandel and Gujarat to Hormuz and the Persian Gulf, and to Aden and the Nile.