Yup, also regret that error. Not “eventually,” but pervasive from the beginning. Few men know the history of the Crusades. Here are two serious works that are helpful, especially in exposing warmongering propaganda so frequently found among Christian nationalists. These men show they know nothing about how many times Latin nations have said the same things about their own homelands, and this for over a thousand years. Such tenderfoots.
First, The Crusades The Authoritative History of the War for the Holy Land, by Thomas Asbridge:
Yet always, at the heart of the crusading impulse, lay the promise of individual salvation: a guarantee that the penalties owing for confessed sins would be cancelled out by the completion of an armed pilgrimage. This was the overwhelming allure of a crusade–its capacity to eradicate the taint of transgression, to offer an escape from damnation. And this was why hundreds of thousands of Latins took the cross in the course of the Middle Ages. (p. 661)
And:
‘Crusade parallelism’ has played a distinct role in shaping the modern world–one that, in recent times, has been widely misunderstood. The manipulation of the history and memory of the war for the Holy Land began with nineteenth-century romanticism and western colonial triumphalism. It has been perpetuated by political propaganda and ideological invective in the Muslim world. The purpose of identifying and examining this process is not to condone or condemn the ideologies of imperialism, Arab Nationalism or Islamism–but rather to expose the crude simplicity and glaring inaccuracy of the ‘historical’ parallels evoked in their name. The political, cultural and spiritual resonances of the distant crusades have been manufactured by an imaginary view of the past; one that trades in caricature, distortion and fabrication, not the medieval realities of reciprocal violence, diplomacy and trade, enmity and alliance that lay at the heart of crusading.
Of course, humankind has always shown a proclivity for the deliberate misrepresentation of history. But the dangers attendant upon ‘crusade parallelism’ have proven to be particularly intense. (p. 680)
From The Crusades A History, Fourth Edition, by Jonathan Riley-Smith and Susanna A. Throop:
As already noted, Portuguese voyages of expansion and “discovery” were undertaken largely by members of the Order of Christ, and the imagery and ideas of crusading were pervasive. Legendary traditions—whether older traditions, like that of Prester John, or newer ones, like that of Manuel I of Portugal as the Last World Emperor—contributed to the perception that European expansion and colonization of lands previously unknown were positive steps toward the Christianization of the world. This was also the goal of theorists like Phillippe de Mézières and formed part of the worldview of the papacy in the fifteenth century.38 And at the same time, others, like Columbus, believed that the wealth generated by their voyages and the conquest and exploitation of those they encountered, would pave the way for “the restitution of the Holy Sepulchre to the Holy Church militant” that was necessary for the End of Days.39 It was also thought possible that finding new routes to Southeast Asia could economically damage the Mamluk Sultanate and thus enable the conquest of Jerusalem. As new lands were conquered by European Christians, the papacy continued its prior practice… (p.602)
And:
The crusading conquest of Ceuta arguably marked the beginning of Portuguese colonies in Africa and the beginning of Portuguese expansion overseas in the Mediterranean, Africa, and India. As Portuguese maritime expansion rolled forward in the fifteenth century, the majority of such voyages were undertaken by members of the Order of Christ, of which Henry the Navigator was the first governor, and ideas and practices of crusading played a central role and ultimately informed Portuguese imperial ideology, as discussed later in the chapter. But with careful attention, even earlier signs are present. The conquest of the Canary Islands, which began in 1403, was launched by two Norman knights on the grounds that the conquest would facilitate the islanders’ Christianization. The earliest accounts of the conquest—which took decades and faced serious indigenous resistance—presented warfare against the islanders as crusading, with papal bulls and banners of the Cross and the Virgin in hand.
In addition, Portuguese activity in West Africa was connected to that in North Africa by the leadership of Henry the Navigator… (p. 563)
And:
Even the Hussites, who were targeted by crusades, nonetheless connected their own religious identity and ideas of Christian holy warfare with Czech nationalism. Norman Housley has concluded that “by the mid-sixteenth century there was scarcely a national, ethnic or civic community in Europe which had not been saluted as a Chosen People, its territory deemed to be sacred soil, and its capital city hailed as the New Jerusalem.”
In discussing the establishment of “sanctified patriotism” in Europe in the fifteenth and sixteenth centuries, Norman Housley has outlined three major conclusions that help us understand the entangled relationship between crusading and nationalism in the fifteenth century. First, the sanctification of the nation relied on the assumption that God would intervene in just wars pro deo et patria (for God and the fatherland) on behalf of his “chosen people.” Second, the soldiers who fought in such wars were a consistent ideological focal point, with their roles elevated well beyond simple military service and seen as deserving and ultimately receiving a heavenly reward. Third, the relationship between crusading and nationalism varied; at times, it was most intimate, as in 1588 when Hapsburg Spain tried to invade England via a formal crusade, while at other moments, the links seem more tenuous. But it is undeniable that the ideas of a nation as a “chosen people” and of soldiers as “soldiers of Christ” would have inevitably evoked the crusades for contemporaries. (p. 599)
If only one, choose Ridley-Smith. Scholarship is deeper.