Morley was in general opposed to ideas that other external groups had influenced the Maya, but in this case, since the conquest occurred in the "degenerate" Post-Classic phase he found it acceptable. This view of the Toltec invasion of Yucatán became the one maintained by the majority of Mayanists. However, recent research from the mid-1990s onwards has now questioned this orthodoxy, to the point where many now hold an actual invasion did not take place, but the similarities in style are largely due to cultural diffusion and trade, and that in fact there is evidence that the diffusion in this period flowed in both directions.