Surprise becomes effective when we suddenly face the enemy at one point with far more troops than he expected. This type of numerical superiority is quite distinct from numerical superiority in general: it is the most powerful medium in the art of war.

[Die Überraschung zeigt sich dadurch wirksam, dass man dem Feinde auf einem Punkt viel mehr Truppen entgegen stellt, als er erwartete. Diese Überlegenheit der Zahl ist von der allgemeinen sehr verschieden, sie ist das wichtigste Agens der Kriegskunst.]

Karl von Clausewitz (1780-1831) Prussian soldier, historian, military theorist
On War [Vom Kriege], Book 6, ch. 2 “The Relations of the Offensive and Defensive to Each Other in Tactics [Wie verhalten sich Angriff und Verteidigung in der Taktik zueinander]” (6.2) (1832) [tr. Howard & Paret (1976)]
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(Source(German)). Alternate translations:

The surprise produces an effect by opposing to the enemy a great many more troops than he expected at some particular point. The superiority in numbers in this case is very different to a general superiority of numbers; it is the most powerful agent in the art of war.
[tr. Graham (1873)]

The suprise produces an effect by opposing to the enemy at some particular point a great many more troops than he expected. The superiority in numbres in this case is very different from the general superiority of numbers; it is the most powerful agent in the art of war.
[tr. Jolles (1943)]