“The Red Army must keep its powder dry and be in constant mobilization and preparedness.”

Popularized by Blacker in the poem "Oliver's Advice", http://books.google.com/books?id=JmEaAQAAIAAJ&dq=%22Oliver%27s+Advice%22+Cromwell&q=%22Oliver%27s+Advice%22+Cromwell#v=snippet&q=%22Oliver's%20Advice%22%20Cromwell&f=false published under the pseudonym Fitz Stewart in The Dublin University Magazine, December 1834, p. 700; where the quote is attributed to Oliver Cromwell (hence the poem's title). The repeated line in the poem is "Put your trust in God, my boys, but keep your powder dry."
Misattributed

Attributed by William Blacker (not to be confused with Valentine Blacker), who popularized the quote with his poem "Oliver's Advice" http://books.google.com/books?id=JmEaAQAAIAAJ&dq=%22Oliver%27s+Advice%22+Cromwell&q=%22Oliver%27s+Advice%22+Cromwell#v=snippet&q=%22Oliver's%20Advice%22%20Cromwell&f=false, published under the pseudonym Fitz Stewart in The Dublin University Magazine, December 1834, p. 700; where the attribution to Cromwell appears in a footnote describing a "well-authenticated anecdote" that explains the poem's title. The repeated line in Blacker's poem is "Put your trust in God, my boys, but keep your powder dry".
Attributed
Variant: Trust in God and keep your powder dry.
Variant: Put your trust in God, but keep your powder dry.

From the poem "Oliver's Advice" http://books.google.com/books?id=JmEaAQAAIAAJ&dq=%22Oliver%27s+Advice%22+Cromwell&q=%22Oliver%27s+Advice%22+Cromwell#v=snippet&q=%22Oliver's%20Advice%22%20Cromwell&f=false by William Blacker, published under the pseudonym Fitz Stewart in The Dublin University Magazine, December 1834, p. 700. This line by a different Colonel Blacker is paraphrased from an attribution to Oliver Cromwell (hence the poem's title).
Misattributed

1910s, Address to the Knights of Columbus (1915)
Context: There must be not merely preparedness in things material; there must be preparedness in soul and mind. To prepare a great army and navy without preparing a proper national spirit would avail nothing. And if there is not only a proper national spirit, but proper national intelligence, we shall realize that even from the standpoint of the army and navy some civil preparedness is indispensable. For example, a plan for national defense which does not include the most far-reaching use and cooperation of our railroads must prove largely futile. These railroads are organized in time of peace. But we must have the most carefully thought out organization from the national and centralized standpoint in order to use them in time of war. This means first that those in charge of them from the highest to the lowest must understand their duty in time of war, must be permeated with the spirit of genuine patriotism; and second, that they and we shall understand that efficiency is as essential as patriotism; one is useless without the other.

Speech to Pilgrims of the United States (16 September 1975) http://www.margaretthatcher.org/document/102462 regarding the Soviet Union
Leader of the Opposition
Context: I am all for the spirit behind this, for easier contacts and the freer movement of people. I am for détente—who is not? I am also for attente, for wanting to see results; for not letting down our guard; for keeping our powder dry. Let them show us that they will practise what they preach, about reducing the threat of war, about non-intervention in the internal affairs of other countries.

Remark to the Austrian Chief of Staff Conrad von Hotzndorf (21 January 1909) during the Bosnian crisis, quoted in L. C. F. Turner, 'The Significance of the Schlieffen Plan', in Paul Kennedy (ed.), The War Plans of the Great Powers, 1880-1914 (Boston: Allen & Unwin, 1985), p. 214

The Independent, Obituaries, Laraine Day, November 13, 2007.

Before the Deluge (1974) from For Everyman (1973)

Source: 1880s, Incidents and Anecdotes of the Civil War (1885), p. 269