World War I centennial events strike somber note

Leaders pledge to remember lessons of conflict in which 10m troops died

World leaders marked the 100th anniversary of the outbreak of World War I on Monday, warning of the lessons to be learned in the face of today's many crises.

"Peace has to be a shared goal," Belgium's King Philippe told leaders gathered in the eastern Belgian city of Liege. "World War I reminds us to reflect on our responsibility ... to bring people together."

Leaders from across Europe - from Britain and Ireland to Germany, Austria, Bulgaria and Malta - attended the commemoration at the Allied War Memorial of Cointe, a tower overlooking the city with a weathered grey-stone church painted with white doves for the occasion.

French President Francois Hollande recalled Germany's invasion of neutral Belgium in early August 1914 that turned a Balkans war into a global conflagration, inviting current-day parallels.

"We cannot remain neutral. ... Europe must live up to its responsibilities with the United Nations," he told an audience that included Britain's Prince William and William's wife, Catherine, Duchess of Cambridge. Also present were heads of state and representatives of about 80 countries.

German President Joachim Gauck said Berlin had launched the war based only on "military logic", and it was immediately apparent that "treaties were worthless and that the standards of civilization had been rendered null and void".

Prince William recalled the German execution of British nurse Edith Cavell, who just before her death in 1915 said: "I must have no hatred or bitterness toward anyone."

"It took another terrible war to learn the truth of her words, and even today we continue to learn that lesson," he said.

The leaders gathered in the industrial town of Liege, built on coal and steel, because it barred the way to invading German troops in the early days of August 1914.

Its fierce resistance derailed Berlin's plans for a quick victory, while Germany's invasion of Belgium formally brought Britain into the war, as interlocking alliances that were meant to preserve the peace plunged Europe into an abyss.

The rest is history - 10 million troops dead, 20 million injured, millions of civilian victims, empires toppled, the world remade.

Earlier on Monday, Australian Prime Minister Tony Abbott and his New Zealand counterpart, John Key, paid tribute to the tens of thousands of their countries' soldiers who died far from home.

The conflict "was the most cataclysmic event in human history," Abbott said.

First British death

Security was very tight in Liege, with all streets leading to the great square and town hall cordoned off, with a heavy police presence.

After Liege, it is the turn of Mons on the French border to remember a do-or-die rear-guard action by the first British troops committed to the war as London and Paris scrambled to prevent a German breakthrough in late August 1914.

Prince William, the Duchess of Cambridge, British Prince Harry and British Prime Minister David Cameron will lead the tributes in Mons, where the first British soldier died.

It was here, too, that the last British soldier was killed on Nov 11, 1918, the day of the armistice that ended hostilities after four bloody years.

The Mons ceremony will focus on the small military cemetery of St Symphorien, where 229 Commonwealth and 284 German solders were buried together in a gesture of reconciliation even as the fighting raged.

Britain, meanwhile, held a series of ceremonies on Monday, with people encouraged to turn off their lights from 10 pm to 11 pm, inspired by then-British foreign secretary Edward Grey's famous remark on the eve of war.

"The lamps are going out all over Europe; we shall not see them lit again in our lifetime," he said.