This was the year the Cold War ended and NATO and the Warsaw Pact signed the most sweeping arms-reduction treaty in history.

The phrase "new world order" gained currency in America as well as Europe. East Germany was merged into West Germany without a flicker of friction. Nations at odds for 45 years were contemplating new arrangements to promote peace and prosperity.So much had the volatile world changed that for a while it seemed the biggest worry in some State Department offices and Washington think tanks was whether new uses could be found for NATO now that U.S.-Soviet tensions had nearly evaporated and military alliances seemed obsolete.

As distrust dissolved, President Bush offered up to $1 billion in food credits to the Soviet Union and other incentives for Mikhail S. Gorbachev to weather dislocations and to keep trying to establish a free-market economy.

Superpower cooperation raised hope, meanwhile, of ending wars in Afghanistan, Angola and Cambodia. Arms sales around the world even dipped a bit.

But as 1991 draws near, the world is not necessarily a safer place.

Gorbachev is trying to hold on to the 15 Soviet republics by taking on new powers that his old friend and ally, Eduard A. Shevardnadze, denounced as a step toward dictatorship.

Shevardnadze resigned as foreign minister, shattering a smooth relationship with Secretary of State James A. Baker III that had promoted reconciliation between Washington and Moscow.

Gorbachev pledged that his foreign policy would be maintained. But that is bound to be harder to do after the resignation of one of its chief architects and amid grumbling in some segments of the military that the Soviets gave in too easily to German unification and to independence in Eastern and Central Europe.

Unrest in the republics poses an even bigger danger to world peace.

Some of the rebellious nationalities are reviving the hateful chauvinism that the central government in Moscow had managed to suppress. Disorder could provoke a heavy-handed response from Gorbachev. He may not be able to cope with separatists on several fronts at once. And that could lead to a splintering of the Soviet Union and the destabilization of Europe.

In the Persian Gulf the threat of war made the whole world anxious.

There is no sign of a diplomatic solution even with the approach of the Jan. 15 deadline set by the U.N. Security Council for Iraq to withdraw its forces from Kuwait.

And President Bush threatens to go to war unless all the troops are not out by then.

`We haven't blinked so far," Brent Scowcroft, his national security adviser, said last week. "We're not blinking now, and we will not blink."

Not to be outdone in bravado, Bush said of Iraqi leader Saddam Hussein: "If we get into an armed situation, he's going to get his ass kicked."

Saddam, meanwhile, threatened to attack Israel and to use all his resources, including chemical weapons.

Perhaps the tough talk on both sides was simply bluster, designed to achieve political objectives. For Bush, that would be the liberation of Kuwait and the restoration of the ousted royal family. For Saddam, that would be at least a piece of Kuwait and the mobilizing of international pressure against Israel.

On the other severely troubled front, maybe Gorbachev will be able to get through the winter with his reconstruction program intact and his drive toward democracy only slightly impeded by the authoritarian measures he has taken.

In the meantime, though, the promise 1990 held out for peace seems more fragile with the approach of the new year.