Italy is looking balefully into a pair of horrors from its wartime past: the use of poison gas by its army to kill off resistance to the invasion of Ethiopia in 1935 and a 1944 massacre of Italians carried out by Nazis in a cave near Rome.

For Italy, the Ethiopian war and Nazi massacre are like historical bookends. Ethiopia represented the squalid glory of Fascist Italy and its imperial pretensions. The massacre nine years later at the hands of German SS troops symbolized the coming end of the bombastic dream:

Italy's powerful German partners had become occupiers and oppressors of the Italians. By war's end, not only was Italy's empire lost, but the country was under control of the Allies and dependent on the generosity of the new conquerors to stay afloat.

Two public events are causing Italians to take stock of this sad trajectory. The first is the recent publication of a book detailing the use of poison gas by the Italian colonial army against the Ethiopians. In advance of publication, the Defense Ministry acknowledged for the first time that the Italian army had used gas in Ethiopia.

The second event is the trial of Erich Priebke, a Nazi SS officer accused of taking part in the execution of 335 Italians at the Ardeatine Caves near Rome, in retaliation for an ambush of Nazi soldiers. He was extradited to Italy from Argentina last year. His trial is scheduled to begin Wednesday.

The Ethiopian adventure and the Ardeatine massacre represent contending faces of Italy's 20th-century history: Italy as bellicose aggressor and perpetrator of war crimes and Italy as victim. It has been important to Italy's post-World War II image as a sound and civilized Western ally to emphasize the role of victim. Much is heard about resistance to Fascist dictator Benito Mussolini among a relative handful of partisans. Little is heard about support for him among the vast majority of Italians.

Forgetfulness about Ethiopia has permitted Italy to play an exaggerated role of moral innocent in foreign affairs since World War II, some Italian historians say. Italians invariably cluck at the involvement in foreign wars by other countries, no matter what the situation: the United States in places as distant as Vietnam and Iraq, for instance.

Historian Angelo Del Boca attributes some of this to an "epidemic of amnesia." "There has not been a government which has favored a serious discussion of what we did in Africa," he told the magazine L'Espresso. "It's said that we don't have in our closet any Vietnam or Algeria, and it's not true. We also have our skeletons."

Although outside Italy it is generally accepted that the Italians dropped poison gas bombs from airplanes, many Italians reject the stories as propaganda. To end the denial, Del Boca edited a book of essays called "Mussolini's Gas: Fascism and the Ethiopia War." It detailed how much and what kind of gas was used in Ethiopia and under what circumstances. Included are texts of telegrams sent by Mussolini to his commander in Ethiopia authorizing the use of gas "on a vast scale."

In February, the Defense Ministry released a document describing the bombing, in which 60 tons of a poison gas perfected in World War I were dropped on Ethiopian soldiers. The release of the document followed an debate between Del Boca and Indro Montanelli, a prominent journalist who served in Ethiopia and who claimed that if gas was used at all, it was only sporadically.

In World War II, Mussolini aligned Italy with Hitler's Germany, a decision that cost the country dearly. In 1943, U.S. and British forces invaded Italy and a group of Italian politicians signed a separate peace. Areas of the country still controlled by the Fascists came under German domination, among them Rome.

In March 1944, someone set off a bomb that killed 33 German soldiers marching on a Roman street. In retaliation, the German SS commander ordered 10 Italians killed for each German. The roundup included suspected members of the Resistance and Jews from the Roman ghetto.

Among those accused of being executioners was Priebke, who escaped to Argentina and lived an open life under his real name. He visited Rome twice as a tourist. Not long ago, he was discovered by a U.S television news team and was interviewed. The discovery created an outcry in Italy, and Rome pressed for extradition.

Priebke's arrival in Rome last November ignited a debate among those who felt it was unseemly to try and jail an 82-year-old man and others who said it was never too late to penalize war crimes. The debate was especially intense within Rome's Jewish community, where a leading rabbi pleaded for clemency, while many members of his congregation argued that Priebke must stand trial. Among the Ardeatine victims, 75 were Roman Jews. "There is no spirit of vengeance," argued Tulia Zeevi, a spokesperson for the Roman Jewish community. "But this is probably one of the last such trials in Europe and it is useful that the details and truth come out."

Priebke's trial will be Italy's first for war crimes since 1948. In that year, Priebke's commander, Col. Herbert Keppler, was convicted and sentenced to life in prison for the Ardeatine massacre. He later escaped from an Italian prison and died abroad. CAPTION: Ex-SS officer Erich Priebke, in Italian police custody, appeared at Rome court in December.