This Supplement to Foreign Relations is the last in the series relating to the World War. The period covered by the volume extends in general from April 6, 1917, when the United States entered the war, to November 11, 1918, the date of the armistice with Germany. The subjects treated were not included in Supplement 2 for 1917 and Supplement 1 for 1918, as they are best considered in their continuous development over the entire period of belligerency.

The general principles followed in compiling the volume are given in the preface to Foreign Relations, 1914, Supplement, pp. iiiiv.

Brackets, [ ], occurring in the text enclose editorial insertions. These are of two main types: (1) words or phrases, in ordinary type, supplied to fill in omissions or replace obviously garbled passages in telegrams; and (2) suggested corrections, in italics, following words or phrases which appear to be incorrect. When there is not sufficient evidence to indicate what has been omitted or garbled, or when the words which might be suggested would so seriously affect the sense of the document that supplying them would involve more than an editorial responsibility, notice is taken of defects in the text by the insertion, within brackets, of “omission,” “garbled groups,” or “sic” Insignificant words are corrected or inserted without distinguishing marks.

Parentheses, ( ), occurring in the text are in the documents themselves. Besides their ordinary use for punctuation, these marks were also employed, in the deciphering and decoding of telegrams, to enclose words or phrases suggested by the decoders as possibly the intended readings of garbled groups which yielded unintelligible or no results. When so employed they have been allowed to stand, unless comparison with other documents showed the suggested reading to have been obviously either correct or incorrect. In the latter case the text within parentheses has sometimes been replaced by an editorial insertion within brackets.

Translations as found in the files have been revised and corrected if found faulty by comparison with texts in the original language or other available versions, but care has been taken to avoid altering in any significant respect important texts that were acted upon or used as sources, of information in their existing form.