Moving swiftly in the darkness, black-clad soldiers scaled the first defensive wall, followed by explosives experts who planned to blow open the city gate to let in their waiting army.

The stretch of Geneva's defenses was poorly guarded, intelligence reports said. By attacking at night the commandos expected to get control of the city before the residents woke up.

But they didn't expect Cpl. Francois Bousezel to sound the alarm. Or quick-thinking Isaac Mercier to drop the heavy iron grill protecting the gate. Or Catherine Royaume to dump a caldron of vegetable soup on their heads.

For 400 years Genevans have commemorated the three-hour battle on the night of Dec. 12, 1602, when their ancestors repulsed Duke Charles Emmanuel of Savoy in his attempt to seize the city.

For the first three centuries they marked the anniversary with a solemn service of thanksgiving, but that has given way to merrymaking.

Formal reenactments of the battle began 100 years ago. Seven hundred enthusiasts, armed with pikes and muskets and wearing 17th-century costumes, march around what is left of the old city walls, watched by a crowd of 80,000.

The reenacters and spectators sing part of "Ce que l'aino," or "The Lord of Hosts," a 68-verse song about the battle in the old Geneva French dialect. Actors playing notables from the period read the original victory proclamation.

Held on the nearest Sunday to the anniversary, the parade -- this year on Dec. 15 -- caps three days of themed events in Geneva's Old Town. The city's museums have special exhibitions continuing into 2003 to commemorate the 400th anniversary.

Other celebrations include an 11-mile race retracing the route taken by the Duke of Savoy's army and a two-mile "fun run" in costume. Earlier this year there was a historical sound and light show.

It's like a combination of Thanksgiving and the Fourth of July, said Olivier Fatio, a University of Geneva expert on the "Escalade," or "scaling of the walls."

"It's really a symbol of our independence and freedom," he said.

Geneva became part of Switzerland only in 1815. For the previous three centuries it was a city-state, known across Europe as the "Protestant Rome" because religious reformer Jean Calvin converted it to his austere brand of Christianity in the 1530s.

After the Reformation the Genevans expelled their bishop, always a member of the family of the dukes of Savoy, and threw out the Catholic Savoy aristocrats.

The affront rankled the family's Charles Emmanuel, who became "obsessed with Geneva," said Fatio. When the 18-year-old rose to the throne of Savoy -- today part of France -- in 1580, he was eager to lift the status of his mountain duchy by seizing the city.

Geneva was a key spot in the period's great power politics because it lay on the military road from Italy to Belgium, both then in the hands of the Spanish. The king of France aimed to stop his Spanish enemies from linking up, so an independent Geneva suited him fine. The Swiss also wanted to protect the shores of Lake Geneva from Savoy expansion.

Charles Emmanuel began a two-decade conflict of blockade and sporadic fighting with the Genevan militia. Treaties were signed and broken.

To seize Geneva itself the Savoy army had to get past the walls protecting the city's 12,000 people.

"They needed about 40,000 men to take Geneva -- if they did it by day," said Fatio. "Or they could attack at night."

Charles Emmanuel's spies said Geneva authorities had grown tired of rumors of war and did not believe an assault would come at night.

After 18 months of planning, the duke assembled a force of 2,000 elite soldiers and marched them into position around midnight on Dec. 11, 1602. The horses' hooves were muffled and the soldiers' armor painted black.

The first 300 men -- mostly aristocrats -- began scaling the outer wall into today's Rue de la Corraterie, a street now home to many of Geneva's exclusive banks.

Around 2:30 a.m., Bousezel, the corporal commanding the watch, heard suspicious noises and went to investigate. When he spotted the invaders, he was able to sound the alarm before being fatally wounded.

As church bells roused the citizens, Isaac Mercier, a soldier at the entrance tower, had the wits to cut the rope holding up the portcullis, a weighty iron grate that dropped to seal the main gate.

Hearing the explosions of the city's cannons firing at the initial wave of attackers, Charles Emmanuel's army mistakenly believed the gate had been breached and marched to battle, only to be driven off in disarray.

Seventeen Genevans were killed. The Savoy side lost 60.

In addition, 13 captured Savoy nobles were executed as brigands. Geneva officials said they had broken an earlier peace deal and were unworthy of treatment as prisoners of war. Their heads were spiked on the walls -- where they remained until the duke signed a peace treaty in July 1603.

After the battle the Genevans held a religious service, giving thanks for what they regarded as divine intervention. The service has been held virtually every year since.

Fatio said the religious element of the Escalade celebration declined in importance in the 19th century. By the late 1800s the emphasis was on having a good time, and city fathers decided Geneva should refocus on its history, giving birth to the annual parade.

"History gets embroidered -- a nighttime event with a spectacular end lends itself to this -- but today it's a sort of unifying festival," Fatio said.

Modern Geneva, with a population of 420,000, is now an international center with residents from all parts of the globe.

Whatever their origin, youngsters don fancy dress at school every Dec. 12, sing songs in class and share "marmites" -- caldrons made of chocolate.

The marmites celebrate the exploits of Catherine Royaume. The best-known Escalade figure, she is remembered for battling Savoy's soldiers from a window in her house on the inner wall.

"We sing songs to celebrate when Mere Royaume tipped a caldron of hot soup on the Savoyards' heads," said 7-year-old Owen Probert, from Britain. "I like the story of the Escalade, and I like dressing up. But most of all, I like the chocolate marmite."