English to Spanish Social Sciences History

Hola.
Hay varias cosas de esta frase que me cuesta comprender, pero específicamente la frase mencionada arriba.
Parte del discurso del Presidente Chester Arthur en su mensaje al Congreso, en 1881:

"It was natural, at a time when the national territory seemed almost illimitable and contained
many millions of acres far outside the bounds of civilized settlements, that a policy should have
been initiated which more than aught else has been the fruitful source of our Indian complications."

¡Gracias por su ayuda!