Definition of "fall upon"

fall upon

verb
third-person singular simple present falls upon, present participle falling upon, simple past fell upon, past participle fallen upon
1. to experience; to suffer.
  Quotations
  Then came a maid with hand-bag and shawls, and after her a tall young lady. She stood for a moment holding her skirt above the grimy steps, […] , and the light of the reflector fell full upon her.
  1897 December (indicated as 1898), Winston Churchill, chapter V, in The Celebrity: An Episode, New York, N.Y.: The Macmillan Company; London: Macmillan & Co., Ltd.
2. to occur at some particular point in time.
  Quotations
  It fell upon the day of full moon of the fourth month, the second year, in the era of Established Calm (AD 168), that Emperor Ling went in state to the Hall of Virtue.
  1925, Charles Henry Brewitt-Taylor, chapter 1, in Romance of the Three Kingdoms
3. to set upon; to attack suddenly
  Quotations
  If the Duke, with the other dukes, come not to composition with the king of Hungary, why then all the dukes fall upon the king.
  c. 1603–1604 (date written), William Shakespeare, “Measure for Measure”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene ii], lines 1-3