The phrase “fleet in being” is one of those troublesome terms that naval historians and strategists have tended to use in a range of different meanings. The term first appeared in reference to the naval battle off Beachy Head in 1690, during the Nine Years’ War, as part of an excuse that Admiral Arthur Herbert, first Earl of Torrington, used to explain his reluctance to engage the French fleet in that battle.
Hattendorf, John B.
"The Idea of a “Fleet in Being” in Historical Perspective,"
Naval War College Review: Vol. 67
, Article 6.
Available at: http://digital-commons.usnwc.edu/nwc-review/vol67/iss1/6