Gabriel Kolko, an influential left-leaning historian who argued that American domestic and international policies have long been driven more by the interests of big business than by the interests of the people, died on May 19 at his home in Amsterdam. He was 81.

He had a progressive neurological disorder and chose euthanasia under Dutch law, said Pim van den Berg, a longtime friend.

In a series of books on turning points in American history, from the westward expansion of the railroads in the 19th century to the Cold War, Vietnam and the war on terrorism, Professor Kolko carved a distinct and sometimes groundbreaking path. He made the case that alliances between government and business, rather than between government and the people, were the essential drivers of regulatory policy, social programs and foreign affairs — an idea that came to be called corporate liberalism.

He was regarded as a cage-rattling New Left historian in the 1960s, and he was active in leftist causes, but over time he provoked thinkers of various stripes. By his late 30s, he had established himself as unconventional. The Pulitzer Prize-winning historian David Herbert Donald called him “a lonely figure among radical historians.”