Joe Sacco is the foremost journalist of English-language comics, a reporter who travels the world to research stories that can be told only by drawing them, such as his 2009 masterpiece “Footnotes in Gaza.” “The Great War,” though, is something different: a single 24-foot-long pen-and-ink drawing. It folds out, accordion-style, to depict the British attack on German trenches on July 1, 1916, the first day of the Battle of the Somme. After a week of nonstop shelling, which they’d been told would all but eradicate the German forces along the River Somme in France, 120,000 British soldiers went “over the top,” beginning at 7:30 a.m. The operation immediately went disastrously wrong. More than 20,000 of them were killed or fatally wounded that day alone.

Sacco’s image itself is wordless; it’s accompanied by a booklet containing the artist’s annotations, along with an excerpt from Adam Hochschild’s World War I history, “To End All Wars.” The drawing is as accurate as possible in its details — artillery, packs, weapons — but impressionistic as a whole. “A few inches in the drawing might represent a hundred yards or a mile of reality,” Sacco notes. What he’s illustrated isn’t a map of the area but an incrementally advancing narrative. At the far left, we see Gen. Douglas Haig’s morning constitutional, followed by howitzer bombardments, the preparations of the night before the attack, the underground mine explosions that signaled the start of the battle and so forth, ending with the lines of wounded outside a casualty clearing station and men erecting a row of crosses alongside a mass grave. The landscape is gradually choked by pointillistically rendered explosions and plumes of smoke.

We can scarcely see the British soldiers’ faces as they trudge through the trenches or writhe on the ground. That’s unusual for Sacco, given his gift for humanizing the people he draws. But he also specializes in showing what photos can’t: the enormousness and the enormity of what happened that day on the Western Front.

Wolk is the author of “Reading Comics: How Graphic Novels Work and What They Mean.”

THE GREAT WAR

By Joe Sacco

Norton. $35