The subtitle of this remarkable popular history is “How FDR and Henry Stimson Brought Democrats and Republicans together to Win World War II”, Stimson being the Republican Franklin Roosevelt chose as secretary of war on 19 June 1940, the same day he chose another Republican, Frank Knox, for secretary of the navy.

Those appointments came five weeks after the king asked Winston Churchill to form a unity government in Great Britain, two weeks after 338,000 French and British troops were rescued at Dunkirk, and four weeks before Roosevelt was nominated for an unprecedented third term, all events featured in this compelling volume.

But Peter Shinkle’s book is a great deal more than a celebration of the bipartisanship that was a key factor in American success. It also offers brisk accounts of all US campaigns in Africa and Europe, a detailed description of how Pearl Harbor happened, and the best explanation I have read of why the government pursued its disastrous policy of interning Japanese Americans.

Besides all that, there is terrific social history of the ways the war changed the status of women and African Americans. Practically the only important social impact Shinkle omits is the war’s effects on gay and lesbian Americans, a subject covered best by Allan Bérubé’s definitive book, Coming Out Under Fire.

Shinkle is a veteran reporter who has written another fine book, Ike’s Mystery Man, about Robert Cutler, the closeted gay man who was Dwight Eisenhower’s right-hand man for foreign policy in the White House. That book also combined political and social history. But his new volume is broader and more important.

There are probably more books written about the second world war than any other 20th-century event, but every generation needs to be reminded of its triumphs and tragedies. Shinkle does a splendid job mining for new nuggets of information and fresh perspectives.

There are two big reasons for focusing on Stimson. Not only did he play a vital role in practically every important military decision from 1940 to 1945, he also kept an extremely detailed diary, which makes it possible for Shinkle to tell us exactly what he was thinking.

Besides canny portraits of Roosevelt, Stimson and George Marshall, the first chairman of the Joint Chiefs of Staff, there are a host of subsidiary characters. The first lady, Eleanor Roosevelt, and Black activist A Philip Randolph are two of the most important heroes while Charles Lindbergh, the celebrated solo pilot to Paris who became a fierce isolationist and a virulent antisemite, is one of its principal villains.

There has been a raging debate for decades about how the surprise Japanese attack at Pearl Harbor came about, and whether Roosevelt and his aides ignored information from Japanese diplomatic cables because they wanted to bring America into the war.

It turns out almost all of the answers are in Simpson’s diary, including this key sentence: “The question was how we should maneuver [the Japanese] into the position of firing the first shot, without allowing too much danger to ourselves.”

One of the biggest problems Roosevelt faced in 1940 and 1941 was how to counter isolationists like Lindbergh, whose affection for the Nazis and hatred for the Jews made him as popular in some quarters as he was despised in others.

Before Congress, Lindbergh denounced the bill that gave Britain resources to survive the Blitz. There was much he didn’t like in the world, but “over a period of years [on both sides] there is not as much difference in philosophy as we have been led to believe”. After the House approved the extension of the draft by a single vote, Lindbergh declared “the greatest danger to this country” posed by its Jewish citizens “lies in their large ownership and influence in our motion pictures, our press, our radio and our government”.

While Roosevelt’s White House denounced that speech for resembling “the outpourings of Berlin”, former president Herbert Hoover “readily defended Lindbergh, a sign of the enduring political power of both the aviator and isolationism”.

That power of these isolationists explains why Stimson did not record “shock, horror or anger” after Roosevelt informed him of the attack on Pearl Harbor. Instead, he wrote, “my first feeling was of relief that the indecision was over and that a crisis had come in a way which would unite our people … For I feel this country united has practically nothing to fear while the apathy and visions stirred up by unpatriotic men have been hitherto very discouraging.”

Roosevelt refused to desegregate the armed forces, largely for fear of alienating southern Democrats. But Shinkle reminds us that Roosevelt’s civil rights record was much more complicated than that failure suggests.

Randolph, who was president of the first important Black union, the Brotherhood of Sleeping Car Porters, used the threat of a March on Washington by 100,000 citizens to pressure Roosevelt into signing a landmark executive order prohibiting discrimination and segregation by military contractors. One activist wrote that the Fair Employment Practice Committee Roosevelt impaneled led to “more progress” against “racial and religious discrimination than [in] any other period in American history”.

Three million women were employed in the defense industry by the end of 1942, as well as new divisions of the army, navy and coast guard, similarly transforming their status.

Jacqueline Cochran commanded the Women Airforce Service Pilots, which graduated 1,100 women training inspectors and test pilots. “Menstrual cycles didn’t upset anyone’s cycle,” Cochran wrote. Women flew “as regularly and for as many hours as the men”.

Shinkle ends with all the ways history is repeating itself today, including a description of “Trump’s fascism”. The resurgence of that hateful ideology, and the budding isolationism of many Republicans eager to end support for Ukraine, are two reasons why this vivid volume is so timely and important.

• Uniting America: How FDR and Henry Stimson Brought Democrats and Republicans together to Win World War II is published in the US by St Martin’s Press