A people may present at any given time only a partial response to their environment also for other reasons. This may be either because their arrival has been too recent for the new habitat to make its influence felt; or because, even after long residence, one overpowering geographic factor has operated to the temporary exclusion of all others. Under these circumstances, suddenly acquired geographic advantages of a high order or such advantages, long possessed but tardily made available by the release of national powers from more pressing tasks, may institute a new trend of historical development, resulting more from stimulating geographic conditions than from the natural capacities or aptitudes of the people themselves. Such developments, though often brilliant, are likely to be short-lived and to end suddenly or disastrously, because not sustained by a deep-seated national impulse animating the whole mass of the people. They cease when the first enthusiasm spends itself, or when outside competition is intensified, or the material rewards decrease. [Sidenote: The case of Spain.] An illustration is found in the mediaeval history of Spain. The intercontinental location of the Iberian Peninsula exposed it to the Saracen conquest and to the constant reinforcements to Islam power furnished by the Mohammedanized Berbers of North Africa. For seven centuries this location was the dominant geographic factor in Spain's history. It made the expulsion of the Moors the sole object of all the Iberian states, converted the country into an armed camp, made the gentleman adventurer and Christian knight the national ideal. It placed the center of political control high up on the barren plateau of Castile, far from the centers of population and culture in the river lowlands or along the coast. It excluded the industrial and commercial development which was giving bone and sinew to the other European states. The release of the national energies by the fall of Granada in 1492 and the now ingrained spirit of adventure enabled Spain and Portugal to utilize the unparalleled advantage of their geographical position at the junction of the Mediterranean and Atlantic highways, and by their great maritime explorations in the fifteenth and sixteenth centuries, to become foremost among European colonial powers. But the development was sporadic, not supported by any widespread national movement. In a few decades the maritime preeminence of the Iberian Peninsula began to yield to the competition of the Dutch and English, who were, so to speak, saturated with their own maritime environment. Then followed the rapid decay of the sea power of Spain, followed by that of Portugal, till by 1648 even her coasting trade was in the hands of the Dutch, and Dutch vessels were employed to maintain communication with the West Indies.[30] [Sidenote: Sporadic response to a new environment.]