PHILADELPHIA — The idea lingers that art can be separated from politics. But it can’t. All art — high, low; illustrative, abstract — is embedded in specific political histories, and direct links, however obscured, are always there. Such links are the unswerving focus of “World War I and American Art” at the Pennsylvania Academy of the Fine Arts, a panoramic show that has the narrative flow of a documentary, and the suspenseful, off-kilter emotional texture of live drama.

World War I lasted roughly four years, from 1914 to 1918, with the United States joining the fray in 1917. The brevity of that engagement has led Americans to play down the war, but we shouldn’t. Although politicians at the time spun the conflict — which the public increasingly understood to be a murderous mistake — as the war that would end all wars, it did the opposite. It set the model for World War II, Vietnam, Iraq. And it departed from previous models of war only in ramping up their barbarities with modern technology.

With World War I, invisibility became a deadly weapon. Submarines turned oceans into minefields. Airplanes, used in regular combat for the first time, killed through stealth and distance. Silent death emerged: poisonous gases enveloped victims, blinding them, eating their flesh, leaving them to drown in their own fluids. Add to these grisly innovations the high-power guns that, dronelike, pulverize bodies outside the range of vision, and you can see how warfare became depersonalized. It felt like a scientific experiment, not a human engagement.