You could not understand them
You could not understand them if I explained them to you, and they are merely two of our smaller developments. I have no serious designs upon the earth nor upon the Solar System, nor have I any desire to rule over, or to control the destinies of masses of futile and brainless men. I have, however, certain ends of my own in view. To accomplish my plans I require hundreds of millions in gold, other hundreds of millions in platinum and noble metal, and some five kilograms of the bromide of radium--all of which I shall take from the planets of this Solar System before I leave it. I shall take them in spite of the puerile efforts of the fleets of your Triplanetary League.
(Text from Triplanetary by Edward Elmer Smith published in Amazing Stories, Jan-Mar 1934. Image made with the blockwave filter from Showfoto, Jun-Aug 2007)