On one level, this was a bucket-list trip to Europe and Russia. On another, it was a trip through history — and its unmistakable implications for the Middle East.

I spent most of May playing tourist in Berlin, Munich, Vienna, Prague, Budapest, Moscow and St. Petersburg, seeing sights missed on visits as a journalist.

But there was no escaping this lesson: It has taken the Europeans centuries to arrive at stable democracy. The Russians are nowhere near it yet — quite the opposite.

So, what about the Arabs? Much as President Barack Obama and the rest of us want to hope for and encourage happy outcomes from the popular rebellions sweeping the Middle East, it would be wise to seriously plan for the worst.

If you visit the palaces and cathedrals of Old Europe, you can’t help but understand why the masses ultimately revolted against their Hapsburg, Wittelsbach, Hohenzollern and Romanoff rulers, who lavished the fruits of workers’ labor on gilded monuments to themselves.

Dazzling as they are — Catherine the Great’s palaces, gardens, crowns, jewels and coaches in and around St. Petersburg, over-the-top them all — the only wonder is why it took until 1918, following World War I, for the empires to be toppled.

The answer, of course, is the same one that accounts for the fact that it’s taken until 2011 for popular uprisings to challenge or topple the dictators of Tunisia, Egypt, Syria, Libya and Yemen — oppression, secret police, goon squads, prohibitions on free speech and assembly, and massacres when necessary.

In Germany, Austria, Hungary and Russia, the revolts that followed World War I resulted either in brief interludes of quasi-democracy or Socialist rule — only to be followed in quick order by either fascist or Communist takeovers.

The horrors of World War I led within a generation to the horrors of World War II, then to Soviet rule over Eastern Europe until Communism’s collapse in 1989.

Germany, Austria and the Czech Republic finally are stable democracies. Hungary is free, too, but the right-wing Fidesz party is imposing worrisome constitutional changes and press laws.

Russia is anything but free. It’s a place where investigative journalists and political foes of Prime Minister Vladimir Putin can easily wind up in jail or dead. Corruption is rife.

Statues of Josef Stalin are out of sight, but those of Vladimir Lenin remain in place. Plans to move Lenin’s tomb out of Red Square are off the table.

So, what does all this tell us about the Arab world? That it’s going to be tough to transition from autocracy to democracy. It’s taken Central Europe, basically, almost a century since 1918 to get it right.

All peoples surely yearn for peace, self-rule and security. But achieving stability requires popular discipline, wise leadership and free institutions that most Arab nations lack.

Of the Arab countries throwing off their despots, Tunisia seems to have the best chance — partly because of its secular tradition and historic connection to France. But, even there, talented people are fleeing and the economy is in danger.

Egypt is the most important country in the region and the signs there are not good.

As David Schenker of the Washington Institute on Near East Policy wrote, “Unprecedented political competition threatens to redound to the benefit of Egypt’s Islamists, a development with potentially grim local and regional implications.”

The big worry is that economic deterioration could aid Islamists, the regional equivalent of Europe’s post-World War I fascists and Communists.

Meantime, despots in Libya, Syria and Yemen are modeling the Russian czars and European monarchs — using brutal force to suppress popular rebellion.

To their credit, Western countries, including the United States, are striving to discourage mayhem and encourage democracy — a departure from the disastrous penalties they imposed on Germany after World War I, paving the way for Adolf Hitler and then Stalin.

NATO is trying to bomb Moammar Gadhafi out of power, and Obama has offered Egypt $2 billion in debt relief and loan guarantees, with other aid promised by the World Bank and Saudi Arabia.

Treatment of Syria, Yemen and Bahrain — despite repression there — has been more permissive, evidently because they are seen as important to the Arab-Israeli peace process, anti-terrorism or U.S. strategy in the Gulf.

Syria is repaying the favor by exacerbating tensions with Israel — encouraging Palestinian demonstrators to charge Israeli border fences, forcing the Israelis to use live ammunition.

Even though the Arab revolutions have not been explicitly anti-Israeli (or anti-American), there’s every danger they could turn that way.

Indeed, Egypt already has opened its border with Hamas-controlled Gaza, and Islamists are agitating to cancel the country’s peace treaty with Israel.

Post-Hosni Mubarak Egypt also promoted the pact between Hamas and Fatah factions in Palestine, which will cause Israel to refuse to negotiate a peace deal.

A crisis could occur this September when Palestine seeks U.N. Security Council recognition as a state — with unanimous Arab support — and the U.S. vetoes it, as Obama has promised.

That could well turn the Arab world sharply hostile — even before it’s determined whether Arab popular revolutions resemble 1989 in Europe, or 1918.