The crisis in Georgia proves once again that the world’s future depends on the lessons it learns from the past. The problem is that there are always too many lessons, and they never exactly fit the current case. As the world’s statesmen try to figure out a way to curb Russian aggression and restore Georgia’s security, a large part of the challenge will be to decide whether 2008 is most like 1938, 1968, or 1878.

1938, of course, was the year of the Munich Agreement, when Britain and France capitulated to German aggression and allowed Hitler to partition Czechoslovakia. What makes Munich such a powerful watchword is not simply the spectacle of two powerful democratic states selling out the weaker democracy they had pledged to protect. More searing is the recollection of Neville Chamberlain brandishing his piece of paper from Herr Hitler, trying to convince himself and the world that it meant a lasting peace. For it was just a matter of months before Hitler broke the terms of the Munich Agreement, swallowing up the remains of Czechoslovakia and turning his sights on Poland. Ever since, Munich has been a reminder that the promises of aggressive dictators are not to be trusted, and that the desire for peace, noble in itself, can become ignoble if it means a desire for peace at any price.

For those who invoke 1938 in the current crisis, the parallels are clear. The enclaves of Abkhazia and South Ossetia, where discontented Russians live under Georgian rule, equal the Sudetenland, where an irredentist German population longed to reunite with Germany. Prime Minister Putin, like Hitler, has used the grievances of this population as a pretext for military action. In this analogy, the role of Chamberlain and Daladier is played by French President Nicholas Sarkozy, who hurried to Moscow to sign an agreement with Mr. Putin, only to find that Mr. Putin had actually agreed to nothing.

It is not clear, however, that even those who propose the 1938 analogy want to follow it through to its logical conclusion. For the lesson of Munich was that the Allies should have fought Hitler when they had the chance — that any apparent peace with the dictator was really just a postponement of war. But you would have to look long and hard for an American commentator who actually thinks we should, or would, go to war for Georgia.

When push comes to shove, America’s response to Russian aggression is actually looking more like 1968. In that year, too, Czechoslovakia was at the center of an international crisis, but this time Soviet Russia was the aggressor. Forty years almost to the day before Russian tanks rolled into Gori, they rolled into Prague, sent to crush the reform movement known as Prague Spring. American diplomats strongly condemned the Russian move, which Brezhnev had described as “fraternal assistance” to the Czech Communist regime. As George Ball, the American ambassador to the U.N., memorably put it, “the kind of fraternal assistance the Soviet Union is according to Czechoslovakia is exactly the same kind that Cain gave to Abel.”

But condemnation was not followed by military intervention. Instead, the West allowed Brezhnev to uphold the division of Europe that had held since 1945, judging that it was too dangerous to challenge the status quo. And in retrospect, it is clear that this passivity was the right choice. It was not worth the risk of a third world war to liberate Czechoslovakia in 1968 when that country would liberate itself, peacefully and lastingly, just 21 years later. If 2008 is 1968, then America’s course ought to follow a hands-off policy, allowing Russia to reassert control over an area that has traditionally fallen into its sphere of influence. We might wish for a free, democratic Georgia, but we would not fight for it, and we would not be surprised if it took generations to emerge.

Neither of these precedents is very encouraging: They seem only to offer a choice between world war and capitulation. Fortunately, history offers another possible lesson, which actually suits the current crisis better than either 1938 or 1968. This is the lesson of 1878 and the Congress of Berlin, which succeeded in halting Russian expansion, thanks to international diplomatic pressure backed up by British military resolve.

The hero of 1878 was Benjamin Disraeli, then in his second term as Britain’s prime minister. For the previous two years, Disraeli — recently named Earl of Beaconsfield — had watched with mounting concern as the Slavic peoples of the Balkans rose up against their Turkish masters, with the support of Tsar Alexander II. It had long been an article of faith for British statesmen that Turkey should be supported against Russia, in order to preserve a balance of power in the Near East. If the Ottoman Empire fell, the British feared that Russia might occupy Constantinople and the Dardanelles, cutting Britain’s link to its Indian Empire.

In April 1877, Russia declared war on Turkey, claiming to be acting in the name of the Sultan’s Orthodox subjects — rather as Mr. Putin now claims to be defending Georgia’s Russians. Disraeli was very apprehensive, fearing that the Russian advance would not stop until it reached Constantinople. Matters were complicated by the fact that Britain, traditionally Turkey’s ally, was in the grips of a popular anti-Turkish passion. Turkish soldiers had recently perpetrated an atrocious massacre against the Bulgarian Christians, in which some 12,000 civilians died. News of the Bulgarian Horrors, as they were called, outraged Britons — including Disraeli’s old rival, William Ewart Gladstone — and led to widespread calls for the Turks to be expelled from Europe once and for all.

Caught between what he saw as the necessities of foreign policy and the demands of public opinion, Disraeli acted with remarkable fortitude. Knowing he could not turn back the Russian advance, he issued an ultimatum: A Russian attack on Constantinople would be considered an attack on vital British interests. He asked Parliament for a credit to mobilize troops, and sent a British fleet to the Dardanelles. He even took the unprecedented — and to his critics, unconstitutional — step of ordering Indian Army forces to Malta. These measures were fiercely opposed even by some members of Disraeli’s own cabinet, and his foreign secretary resigned in protest.

But the event justified Disraeli’s hard-line stance. The Russian armies halted their advance before Constantinople, and in the end, the Tsar agreed to an international conference to decide on Turkey’s postwar borders. In the summer of 1878, Disraeli was the star of the Congress of Berlin. (He was especially gratified to find all the diplomats’ wives reading the romantic novels he had written in his youth.) And when he returned to London, he was given a hero’s welcome, with huge crowds escorting him from the train station back to 10 Downing St.

It is little remembered now, but in 1938, Neville Chamberlain was actually alluding to Disraeli’s triumph when he claimed that the Munich Agreement would bring “peace with honor.” What Chamberlain told the crowds outside Downing Street was: “My good friends, for the second time in our history, a British Prime Minister has returned from Germany bringing peace with honor.” The first time, all Britons would have remembered, was in 1878, when Disraeli stood at the same spot and said: “Lord Salisbury and myself have brought you back peace, but a peace, I hope, with honor, which may satisfy our sovereign and tend to the welfare of the country.”

Will the world find a way to achieve peace with honor in Georgia? It is still too soon to tell. But the lessons of 1878 are clear. Disraeli recognized the limits of what British force could achieve — he did not seek to reverse the verdict of the Russo-Turkish war. But he identified Britain’s vital national interest — the freedom of the Straits — and he was genuinely willing to risk war in order to secure it. Most important, he made clear to Russia that his threat was credible. This combination of pragmatism and principle gave Disraeli the greatest triumph of his checkered career, and demonstrated the importance of what he called “that force which it is necessary to possess often in great transactions, though fortunately you may not feel that it is necessary to have recourse to that force.”

Mr. Kirsch’s biography of Benjamin Disraeli will be published next month by Nextbook/Schocken.