"A Difficult Undertaking" is a short story by Harry Turtledove, set in his Videssos Series. It was the first published entry in the series. It was originally published in September 1986 in The Dragon. It was reprinted in 1988 in Robert Adams' Book of Soldiers and again in 1990 in Kaleidoscope. The story is set between The Tale of Krispos and the Legion Cycle on the island of Kalavria. It tells the story of a siege by the Videssians under the command of Kypros Zigabenos of the citadel of Sotevag, controlled by the Halogai led by Ulror Raska's son.
In Kaleidoscope, Turtledove states that the story is based on a writing of historian Anna Comnena, without specifying further.