Thou knowest that since the invention of gun-powder, there is no place impregnable: that is to say, Usbek, there is no longer any asylum upon earth against injustice and violence. I always tremble for fear at last some invention will be found out of a shorter way to destroy mankind, and to depopulate whole nations and whole kingdoms.

[Tu sais que, depuis l’invention de la poudre, il n’y a plus de places imprenables ; c’est-à-dire, Usbek, qu’il n’y a plus d’asile sur la terre contre l’injustice et la violence. Je tremble toujours qu’on ne parvienne à la fin à découvrir quelque secret qui fournisse une voie plus abrégée pour faire périr les hommes, détruire les peuples et les nations entières.]

Charles-Lewis de Secondat, Baron de Montesquieu (1689-1755) French political philosopher

Persian Letters [Lettres Persanes], Letter 106, Rhedi to Usbek (1721) [tr. Ozell (1760 ed.), # 105]
    (Source)

(Source (French)). Alternate translations:

Thou knowest, that since the Invention of gun-powder, there is no place impregnable; that is to say, Ushek, that there is not any longer an asylum upon earth against injustice and violence. I always tremble, left they should at arrive at last, at the discovery of some secret, which may furnish them with a shorter way to destroy mankind, and to depopulate whole nations and whole kingdoms.
[tr. Floyd (1762), # 105]

You know that since the invention of gunpowder no place is impregnable; that is to say, Usbek, that there is no longer upon the earth a refuge from injustice and violence. I dread always lest they should at last discover some secret which will furnish them with a briefer method of destroying men, by killing them off wholesale in tribes and nations.
[tr. Davidson (1891)]

You know that, since the invention of gunpowder, no fortress is impregnable; that is to say, Usbek, that there is no longer upon earth an asylum against injustice and violence. I am always in terror lest some secret or other should be at length discovered that will not only kill men, but destroy entire tribes and nations.
[tr. Betts (1897)]

You know that since the invention of gunpowder there have been no impregnable places; and this is to say, Usbek, that there is no longer an asylum from injustice and violence any¬ where on the earth. I am in constant terror that ultimately someone will succeed in discovering some secret which will furnish an even more efficient way to kill men, by destroying whole peoples and entire nations.
[tr. Healy (1964)]

You know, since the invention of gunpowder, no fortification is impregnable; in other words, Usbek, there no longer exists, anywhere on earth, any asylum from injustice and violence. I live in fear that men of science will eventually discover some secret which would offer a faster day to kill people, destroy races, and wipe out entire nations.
[tr. Mauldon (2008)]

You know that since the invention of gunpowder, no place is impregnable -- and that is to say, Usbek, that there is no place on earth where we are safe from injustice and violence. I tremble at the thought that eventually someone will discover some new secret that will lead to an even more efficient way to kill even more people, perhaps to destroy entire populations and nations.
[tr. MacKenzie (2014), # 105]