This title is a misnomer, sometimes you need to write War and Peace but many times you don’t. In fact, you probably should leave War and Peace to Tolstoy. What I wanted to get across is the idea of managing complexity. Make certain that your making your story only as complex as it needs to be to accomplish your goal.
In writing, we have the idea of Purple Prose, which I will explain by two examples,
But the Quincunx of Heaven runs low, and ’tis time to close the five ports of knowledge. We are unwilling to spin out our awaking thoughts into the phantasms of sleep, which often continueth precogitations; making Cables of Cobwebs and Wildernesses of handsome Groves. Besides Hippocrates hath spoke so little and the Oneirocriticall Masters, have left such frigid Interpretations from plants that there is little encouragement to dream of Paradise it self. Nor will the sweetest delight of Gardens afford much comfort in sleep; wherein the dullness of that sense shakes hands with delectable odours; and though in the Bed of Cleopatra, can hardly with any delight raise up the Ghost of a Rose. -Sir Thomas Browne (1658)
It was a dark and stormy night; the rain fell in torrents—except at occasional intervals, when it was checked by a violent gust of wind which swept up the streets (for it is in London that our scene lies), rattling along the housetops, and fiercely agitating the scanty flame of the lamps that struggled against the darkness. -Edward Bulwer-Lytton (1830)
In both cases the authors seem much more concerned with applying literary flourishes than they are with storytelling. The primary goal of a story is to convey information effectively and most of the times that means conveying it concisely. Unless of course you’re gunning for the Bulwer-Lytton fiction writing prize.