European countries feared their own fifth columns. Here, authorities in London round up resident Germans and send them back to their native country. Bettmann/Corbis

If there are 9 millions of German birth or descent [in the United States], 3 millions of Scandinavian, 1.5 millions of French, more than 2 millions of Italian, 10 millions of English, the extent to which their presence weakens the country becomes a matter of the first magnitude. The strength of the tie of allegiance to the United States as against the country of their origin, in case of life-and-death struggle between the two, is something which the individuals themselves are wholly incapable of estimating in advance. It depends upon the extent to which the old ties have been weakened and the new ties formed here. It depends upon the extent to which the German, French, Russian, Italian, English characters have been erased and American traits developed in their place …

Allegiance is a matter of psychology, quite as much as of law. In short, it is simply a question of the thoroughness with which the melting pot has done its work. Until the nationality of the immigrant and his descendants has been melted and recast, he is still at heart a foreigner; he is an element of weakness and disunion, and to that extent he will be a traitor to his adopted country whenever that country comes to death-grips with the land of his birth.

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