From all this, the shortcomings of the Spanish attempts at a protective system are sufficiently evident.

In view of the hostile reception extended to them in all parts of the Continent by the Spanish officials, it was only to be expected that foreigners, whenever they had the opportunity, should have rendered a whole-hearted assistance to this business of smuggling. Moreover, since there was seldom peace between the Portuguese and the Spaniards, the former were only too glad to foster this trade, and thus defeat the object of the Spanish authorities, and incidentally line their own pockets. It was all the more difficult for the Spanish Colonial Government to maintain a consistent attitude when the introduction of the slaves, on whom the welfare of so many districts depended, was in the hands of foreigners.

This state of affairs applied in a far lesser degree to Brazil, since that country was frequently able to obtain its human consignments in Portuguese vessels from its fellow-colony of Portuguese West Africa. The Spaniards, on the other hand, were dependent upon other nations for the importation of their slaves, and they were from time to time accustomed to grant special licences for this purpose. It was the reverse of likely that men of a temperament which urged them to raid the African shores in search of their human quarry, and to sail their black cargoes through the tropics, would abstain from making the fullest and most general use of an opportunity thus offered, as the Spanish officials invariably found was the case to their cost, and occasionally, as has been said, to their profit!

The rivalry which characterized the relations between Spain and Portugal did not fail to be carried across the ocean, nor, when transferred to the colonies of either nation, did the mutual jealousies grow less bitter. Indeed, scarcely had the colonization of Brazil and of the Spanish territories commenced in earnest when the struggle between the two nationalities began.

The area of the strife, fortunately, was confined. The enormous territories of tropical Brazil forbade anything in the nature of thorough exploration on the part of the few and slender bands of the pioneers, to say nothing of any attempt at expansion. It was in the south, where the narrow strip of Brazil projected itself downwards into the temperate latitudes, that the desire for aggrandizement raged. The Portuguese considered that the natural southern frontier of their great colony was the River Plate. The Spaniards, having already possession of the northern bank, fiercely resented any such pretension, with the result that the Banda Oriental, by which name the Republic of Uruguay is still locally known, as well as the southern part of the Province of Paraguay, became the scene of many battles. It may be said that the warfare between the two nations continued here, with but rare and short peaceful interludes, for centuries.

The fortified town of Colonia, on the north bank of the Uruguay River, represented one of the chief bones of contention. Its possession constituted a strategic advantage of no small importance, and Spanish and Portuguese flags waved alternately over its shattered ramparts. The situation was accentuated by the characteristics of the inhabitants of the Portuguese city of São Paolo. These people, who lived in the town loftily placed upon its rock, had acquired for themselves, almost from the inception of the colony, a somewhat sinister and reckless reputation. The Portuguese and half-breeds here, their vigour unimpaired by a temperate and bracing climate, would sally out to the west and to the south on slave-raiding expeditions, which they conducted with extraordinary ferocity and enterprise. Matters of boundaries and frontiers possessed no interest whatever for these Paolistas or Mamelucos, by which latter name the swashbuckling members of this community were better known.

In the first instance, these forays were responsible for comparatively little friction, since the number of Indians near at hand was as plentiful as the neighbouring white men were rare. When the nearer land became depopulated, however, it began to be necessary to extend the expeditions farther afield from São Paolo, and it was then that the Mamelucos came into contact with the growing numbers of the Spanish settlers, and with the Indians who now resided beneath the protection of the Spanish power. When the Jesuit missionaries arrived in Northern Uruguay and in Southern Paraguay their advent had the effect of embittering the feud between the frontiersmen; for the Jesuits, forming the Indians into companies of their own, withdrew them still farther from the onslaughts of the Paolistas. These latter determined at all costs to capture and to drive back their gangs of slaves, became more and more emboldened, and pushed forward to the south and west well into the Spanish territories, harrying the missionary settlements, and laying waste the countryside.

For years the Guaraní Indians, unarmed, were helpless in the face of such attacks. Eventually, however, the influence of the Jesuits obtained permission from the Court of Spain for these latter to be provided with firearms, and after this the Indian regiments, trained and disciplined, offered such effective resistance to the Mamelucos that these were forced to cease their slave-raids.

In 1574, when the importation into Brazil of negro slaves from West Africa had become a regular affair, the demand for slaves on the part of the Paolistas naturally became less active. Even with this item of discord removed, such intervals of peace as were patched up between the rival Powers were of short duration. The fertile and temperate lands to the north of the River Plate still remained in dispute, and although the Spaniards succeeded in retaining the possession of the bulk of these, there were times when the Portuguese penetrated as far as the waters of the great river, and in the end they managed to detach several of the most northerly districts from Spanish control, and in adding these to their own colonies.