Ramon Llull devoted at least three works to the highly detailed explanation of how his new model for missionary work should be put into practice. These works are the Tractatus de modo convertendi infideles (1292), the Liber de fine (1305) and the Liber de acquisitione Terra Sanctae (1309). Another, shorter, work could also be added, namely the Quomodo Terra Sancta recuperari potest (1292), which offers other interesting details. The three works we have mentioned consider the same themes, although with some, possibly strategic, variation, corresponding chiefly to the political changes of the period.
If one follows the example of the Liber de fine, the most important theme is that of preaching. Llull’s reference to the “apostolic model” and to the foundation of missionary colleges gives rise to a consideration of the addressees of the missions: Muslims, Jews, Eastern Christians and the Tartars or gentiles.
The second theme is that of military crusades. The three main aspects considered are those of the overall commander of the crusade, the composition of the military force and the route to be taken by the expedition. While Llull’s evaluation of the military force required coincides in all three works, there are important changes in the other two stipulations. The two texts from 1292 seem to grant overall command of the crusades to the Master of a new military order, resulting from the unification of the existing orders. The Liber de fine, on the other hand, speaks of a “warrior king” (“rex bellator”), something which is explicitly rejected in its turn in the text of 1309.
As regards the journey to be made, the Tractatus proposes the eastern route, that is to say, via Greece, Armenia and Syria. The Liber de fine, once the other alternatives have been examined, sees the only advisable route as being via Hispania [former Roman province including modern-day Spain and Portugal] and North Africa. The Liber de acquisitione, lastly, returns to the eastern route and recommends the capture of Constantinople, adding to this also, however, a plan for the conquest of Ceuta as a gateway towards the occupation of North Africa.
Source: J. Gayà, Introducció in R. Llull, Darrer llibre sobre la conquesta de Terra Santa (Barcelona: Proa, 2002), pp. 62-63.