The proverb has been attributed to both Napoleon and Frederick the Great; this figurative use of (on one's) stomach is unusual in English.

‘An army marches on its stomach.’ ‘C'est la soupe qui fait le soldat.’ These Napoleonic aphorisms‥have been increasingly appreciated by our War Office.
[1904 Windsor Magazine Jan. 268]

‘They say an army marches on its stomach,’ Gilbert Slack began to say. ‘You mean that Frank was a cook?’
[1977 J. B. Hilton Dead-Nettle x.]

‘Didn't see service as such. Supply and demand myself. Pay and personnel. Laundry and so forth. An army marches on its stomach.’
[1992 W. Donaldson Root into Europe ii.16]

‘An army marches on its stomach.’ ‘And retreats on its‥’
[2002 Washington Times 30 Jan. E4 (Hazel comic strip)]

Related to: food and drink; soldiers

Bibliography of major proverb collections and works cited from modern editions is available here.

The Oxford Dictionary of Proverbs. Copyright © 1982, 1992, 1998, 2003, 2004 by Oxford University Press. All rights reserved.