What is "to spring upon"

Spring \Spring\ (spr[i^]ng), v. i. [imp. Sprang (spr[a^]ng) or Sprung (spr[u^]ng); p. p. Sprung; p. pr. & vb. n. Springing.] [AS. springan; akin to D. & G. springen, OS. & OHG. springan, Icel. & Sw. springa, Dan. springe; cf. Gr. spe`rchesqai to hasten. Cf. Springe, Sprinkle.]

1. To leap; to bound; to jump.

   The mountain stag that springs From height to height, and bounds along the plains.
   --Philips.

2. To issue with speed and violence; to move with activity; to dart; to shoot.

   And sudden light Sprung through the vaulted roof.
   --Dryden.

3. To start or rise suddenly, as from a covert.

   Watchful as fowlers when their game will spring.
   --Otway.

4. To fly back; as, a bow, when bent, springs back by its elastic power.

5. To bend from a straight direction or plane surface; to become warped; as, a piece of timber, or a plank, sometimes springs in seasoning.

6. To shoot up, out, or forth; to come to the light; to begin to appear; to emerge; as a plant from its seed, as streams from their source, and the like; -- often followed by up, forth, or out.

   Till well nigh the day began to spring.
   --Chaucer.

   To satisfy the desolate and waste ground, and to cause the bud of the tender herb to spring forth.
   --Job xxxviii. 2

7. Do not blast my springing hopes.
   --Rowe.

   O, spring to light; auspicious Babe, be born.
   --Pope.

   7. To issue or proceed, as from a parent or ancestor; to result, as from a cause, motive, reason, or principle.

   [They found] new hope to spring Out of despair, joy, but with fear yet linked.
   --Milton.

8. To grow; to thrive; to prosper.

   What makes all this, but Jupiter the king, At whose command we perish, and we spring?
   --Dryden.

   To spring at, to leap toward; to attempt to reach by a leap.

   To spring forth, to leap out; to rush out.

   To spring in, to rush in; to enter with a leap or in haste.

   To spring on or To spring upon, to leap on; to rush on with haste or violence; to assault.