The years of World War II represent the most paradoxical era in the history of the Supreme Court. There have been periods of conservative ascendency at the Court (many of them), as well as liberal interludes (very few), but the war years produced a dizzying mix of decisions in which no clear ideological direction prevailed. In The Court at War: FDR, His Justices, and the World They Made, Cliff Sloan explores this slice of the Court’s history and does an admirable job of untangling the crossing strands of the decisions. It’s a fascinating tale on its own terms, full of big issues and personalities. And despite the passage of the decades, the book also offers important lessons for the vexed current moment at the Supreme Court.

The war followed perhaps the most precarious time in the history of the Court. After Franklin D. Roosevelt became President in 1933, he joined with the huge Democratic majorities in Congress to pass dozens of pieces of legislation designed to ameliorate the Great Depression. Opponents of the New Deal filed legal challenges to virtually all of these laws, and the Supreme Court began ruling against FDR, over and over again. Between 1935 and 1936, the Court struck down the National Industrial Recovery Act, which was the centerpiece of Roosevelt’s economic program; the Agricultural Adjustment Act; the Federal Farm Bankruptcy Act; the Railroad Retirement Act; and the Bituminous Coal Conservation Act. The Court even overruled a New York law that set a minimum wage for women and children. In most of these cases, the opposition to Roosevelt’s programs was led by four reactionary and elderly justices—Pierce Butler, James Clark McReynolds, George Sutherland, and Willis Van Devanter—who were known as the Four Horsemen. Because they were usually joined by Justice Owen Roberts, a Herbert Hoover appointee, the New Deal faced what appeared to be an implacable wall of opposition at the Court.

Stymied by the Court in his efforts to address the Depression, which was still affecting millions, Roosevelt cast about for a way to circumvent the justices. At the time, economic distress was fueling the rise of fascism in Europe, and FDR felt the same kind of risk existed here if his government couldn’t respond effectively. In desperation, in 1937, he proposed what became known as the “court-packing plan,” one of the most controversial acts of his presidency. It would have allowed the President to add one new justice for each sitting justice over the age of 70, giving Roosevelt up to six new appointments and forcing the “horsemen” into the minority. At around the same time, though, Justice Roberts, who had previously opposed FDR, voted to uphold the constitutionality of minimum wage laws in West Coast Hotel Co. v. Parrish. Roberts’s change of heart gave Roosevelt an effective majority on the Court and took the air out of the court-packing plan; thus, Roberts’s vote became known as “the switch in time that saved nine.” In any event, between 1937 and the American entry into World War II, seven justices—nearly the entire Court—retired or died, and Roosevelt appointed their replacements. In June 1941, when Sloan’s story begins, the New Deal was safe from judicial assault, and Roosevelt could rely on a dedicated and compliant majority of justices.

Sloan is now a professor at Georgetown University Law Center, which he joined after a long career as a corporate lawyer and sometime government official. He served, for a time, as President Obama’s designee in the efforts to close the detention center at Guantanamo Bay in Cuba. That experience must have enriched his understanding of the difficulties of preserving the rule of law under the political stresses of wartime. (In the late 1980s, Sloan and I were colleagues on the staff of Lawrence E. Walsh, the Iran-Contra independent counsel. We have been friendly over the years, though I didn’t know he was writing this book until it was published.)

The Court at War is best read alongside two classics of Supreme Court history. In Supreme Power, author and former Bill Clinton speechwriter Jeff Shesol tells the story of the crisis of the 1930s at the Court—the judicial assault on the New Deal and the President’s response. For the most part, the court-packing plan has been seen as a low point in FDR’s presidency—an unseemly power grab—but Shesol is more sympathetic, considering the magnitude of the country’s problems at that point and the existential threats to democracy if Roosevelt failed. In Scorpions, Noah Feldman of Harvard Law School provides a group biography of four of FDR’s appointees to the Court—Felix Frankfurter, William O. Douglas, Hugo Black, and Robert Jackson. These were days when leading an eventful public life served as a qualification to serve on the Supreme Court, in contrast to today, when a long paper trail is a liability. Through Feldman’s lens, the lives of his quartet serve not only as a window on the Court’s history but also the country’s from the 1930s to ’70s.

Sloan’s focus is narrower—on the war years alone. Since Roosevelt had essentially appointed the whole Court, the key battle of the 1930s over the scope of federal power ended quickly; all of the Roosevelt justices embraced a conception of the Constitution that essentially gave the federal government carte blanche to regulate the economy. But when it came to civil liberties, there were real divisions, as best demonstrated by the flag salute cases. In 1940, in Minersville School District v. Gobitis, the Court upheld the expulsion of two young Jehovah’s Witnesses who had refused to join their public school’s mandatory flag salute in their Pennsylvania town. The vote was 8-1, with five Roosevelt appointees—Black, Frankfurter, Douglas, Stanley Reed, and Frank Murphy—joining Chief Justice Charles Evans Hughes as well as Roberts and McReynolds. Only Harlan Fiske Stone, a Coolidge appointee whom FDR later elevated to chief justice, dissented. Frankfurter, who wrote the opinion, justified the result by associating it with the Court’s new deference to the decisions of legislators. A few weeks later, Frankfurter said that, in the same way that the Court was no longer stopping the New Deal laws, “It was not the business of the court to set itself up as a local school board or to overrule the judgment of the legislature.” Moreover, at a time when the United States had not yet entered World War II, the conflict was going poorly for its allies; the opinion came down on the day the last British soldier had been evacuated from Dunkirk. As Sloan recounts, Frankfurter believed that his decision would help foster “national unity” at this perilous moment. In fact, the opposite occurred. The decision inspired “a wave of violence against Jehovah’s Witnesses.” By the end of 1940, more than 1,500 Witnesses had been assaulted in 350 attacks.

Then came U.S. entry into the war. By this point, FDR had added another justice: Robert Jackson, a longtime Roosevelt ally from western New York, who had already served the President in a variety of roles, including as attorney general. Jackson never went to college and apprenticed in a law office rather than graduate from law school—not an uncommon way of becoming a lawyer in his day—and he turned out to be the finest prose stylist in the Court’s history. In 1943, the Court agreed to hear a case from West Virginia that was nearly identical on its facts to Gobitis; but this time, the Court ruled for the students, 6-3. Three justices (Black, Douglas, and Murphy) flipped their votes, joining Stone, Jackson, and another newcomer, populist Wiley Rutledge.

What caused this change, which remains one of the fastest reversals of a precedent in the Court’s history? The tide of the war had begun to turn, thanks principally to the Soviet Union’s victory in the Battle of Stalingrad. The magnitude of Nazi evil had come into clearer focus, and Roosevelt had begun to spell out his aims for the postwar world, starting with his Four Freedoms speech in 1941. Those goals turned into the Atlantic Charter—the foundation of the U.S. alliance with Great Britain—and “freedom of worship” occupied a central position. All those influences went into Justice Jackson’s opinion in West Virginia State Board of Education v. Barnette, which remains among the most eloquent in the Court’s history.

Jackson drew a direct analogy between the oppression of minorities by our adversaries in the war and West Virginia’s attempt to crack down on the Witnesses: “Ultimate futility of such attempts to compel coherence is the lesson of every such effort from the Roman drive to stamp out Christianity…down to the fast failing efforts of our present totalitarian enemies. Those who begin coercive elimination of dissent soon find themselves exterminating dissenters.” The peroration of Jackson’s opinion remains a classic on freedom of thought and worship:

[F]reedom to differ is not limited to things that do not matter much. That would be a mere shadow of freedom. The test of its substance is the right to differ as to things that touch the heart of the existing order. If there is any fixed star in our constitutional constellation, it is that no official, high or petty, can prescribe what shall be orthodox in politics, nationalism, religion, or other matters of opinion or force citizens to confess by word or act their faith therein. If there are any circumstances which permit an exception, they do not now occur to us.

The Barnette decision seemingly committed the Court to an embrace of diversity and of difference. But then, just seven days after Barnette, the Court upheld the criminal conviction of Gordon Hirabayashi for “being a person of Japanese ancestry” who failed to report for his evacuation and internment. As Sloan aptly observes, “In the course of one week in the midst of the war, the Roosevelt Court issued one of the Court’s staunchest defenses of civil liberties—and one of its greatest betrayals of civil liberties.”

The Hirabayashi case was followed by Korematsu v. United States, in 1944, a very similar case in which the Court, by 6 to 3, upheld the criminal conviction of an American citizen of Japanese descent for failing to report for internment. The two cases have long been regarded as dismal lowlights in the history of the Court, but in Sloan’s telling, the justices, as well as the Roosevelt Administration, manage to look even worse than one imagines. In its brief to the Supreme Court in Korematsu, FDR’s Justice Department relied on a demonstrably false report that asserted there was proof of espionage by Americans on the West Coast—a legal move that was, according to Sloan, “a historic and shameful failure by the best and brightest of the American legal establishment.” Black’s opinion for the Court reflected a willful blindness to the racism in the government’s treatment of an American citizen. “Korematsu was not excluded from the Military Area because of hostility to him or his race,” Black wrote. “He was excluded because we are at war with the Japanese Empire, because the properly constituted military authorities feared an invasion of our West Coast and felt constrained to take proper security measures.” Jackson, who dissented along with Roberts and Murphy, was unsparing in response: “Korematsu was born on our soil, of parents born in Japan,” he wrote. “No claim is made that he is not loyal to this country…. Here is an attempt to make an otherwise innocent act a crime merely because this prisoner is the son of parents as to whom he had no choice, and belongs to a race from which there is no way to resign.”

The majesty of Barnette and the disgrace of Korematsu are perhaps best explained by the subtitle to Sloan’s book: “FDR, His Justices, and the World They Made.” In this period, the Court’s virtues and flaws replicated Roosevelt’s own. In part, this happened because the justices of this era operated with a pre-Watergate sense of ethical constraints. Douglas and Jackson were two of Roosevelt’s regular poker buddies; Frankfurter also remained a friend and adviser, and so, to a lesser extent, did Reed. Roberts agreed to FDR’s summons to lead an investigation of Pearl Harbor. In a reference to Frankfurter and Douglas, Roosevelt in 1945 asked his attorney general, Francis Biddle, to “slip a word to Felix or Bill” about a pending case. To contemporary eyes, the Roosevelt justices remained in unseemly thrall to their patron.

But it wasn’t just Roosevelt’s lobbying that produced the results he wanted. FDR was sensitive to civil liberties and civil rights concerns, but only to a limited extent, and the same was true of “his” justices. During the war, the Court took a few tentative steps in the direction of racial justice. In 1944, for example, the Court struck down the Texas Democratic Party’s practice of prohibiting Black people from voting in primary elections. But Roosevelt was reliant on the Southern wing of the Democratic Party, which meant that he tread lightly (or not at all) on the road to racial equality. As the historian Ira Katznelson demonstrated in his book Fear Itself, the New Deal was crafted to alleviate the Depression without undermining Jim Crow; Roosevelt’s justices, at least during the war, operated the same way. And during that time, the Supreme Court, like the President, put victory over Germany and Japan ahead of any other objective. That, ultimately, is the best explanation for Korematsu: If the commander in chief said a policy was necessary to win the war, a majority of the justices were going to stand up and salute, regardless of the consequences for its innocent victims or the Court’s reputation.

Sloan largely confines his narrative to the Court during World War II, but some connections—and, more to the point, some contrasts—with today’s Court are unavoidable. Sloan’s justices, for example, did not pretend that they operated at an Olympian remove from the events of their day, especially the war. When Jackson, in Barnette, referred to “the fast failing efforts of our present totalitarian enemies,” he wasn’t just cheerleading for the Allies. He was acknowledging that the war had taught the Court an important lesson about the necessity for tolerance. (The three justices who changed their votes after Gobitis apparently felt the same way.) Implicit in this perspective was the idea that the Constitution, and thus the Court, had to respond to the challenges of modern life, in both peace and wartime. Even when FDR’s justices were coming up with the wrong answers, they were asking the right questions. What should the Constitution mean today, they asked—rather than, what did the Constitution mean when it was written a century and a half earlier?

In other words, Sloan’s book offers a useful critique of originalism, the fashionable conservative approach that holds that the words of the Constitution must be interpreted according to their “original public meaning.” Justices in this school, most notably Clarence Thomas, burrow into eighteenth-century sources in order to divine precisely what James Madison and those around him would have thought about such issues as abortion and affirmative action. They pretend that the Constitution and their own duty are timeless, unaffected by the events and values of modern life. For the justices of the FDR era, now nearly a century in the past, that approach would have been laughable; even Hugo Black, often regarded as the father of originalism, didn’t interpret the Constitution this way. For example, in Black’s most famous opinion, Gideon v. Wainwright, he held that the government always had to provide lawyers for indigent criminal defendants. This was true not because the Framers required it—they didn’t, in fact—but because such a rule was necessary “to achieve a fair system of justice.” Black and the other justices in Sloan’s book sought to apply broad principles like due process and equal protection to the problems of their day. They understood that it wasn’t just permissible, but mandatory, to adapt these concepts to contemporary issues.

A total war stresses every institution in a combatant country, and that was certainly true of the Supreme Court during World War II. In The Court at War, Sloan offers clear, fair judgments not with the false surety of hindsight, but based on the circumstances of the justices at the time. His verdict reflects a melancholy truth about the justices in wartime—and pretty much any other time. They are no better, and probably no worse, than the citizens over whom they preside.