The United Nations on Monday marked its 75th anniversary with an appeal from Secretary General Antonio Guterres to preserve the longest period without military conflict between world powers in modern history.

The UN chief addressed a virtual gathering of diplomats and officials, saying “it took two world wars, millions of deaths and the horrors of the Holocaust for world leaders to commit to international co-operation and the rule of law”, and that commitment produced results.

“A Third World War – which so many had feared – has been avoided,” Mr Guterres said. “This is a major achievement of which member states can be proud – and which we must all strive to preserve.”

Appealing for the world’s nations and peoples to work together, Mr Guterres said, “the Covid-19 pandemic has laid bare the world’s fragilities” which can only be addressed together.

“Today we have a surplus of multilateral challenges and a deficit of multilateral solutions,” the secretary general said.

While the UN hosts its 75th General Debate, giving a platform for presidents, prime ministers and kings to address the globe, the event this year will be like no other. Hosted largely virtually due to the coronavirus pandemic, most leaders will make speeches by video.

Looking back over the past 75 years, Mr Guterres cited other major UN achievements: peace treaties and peacekeeping missions, decolonisation, setting human rights standards, “the triumph over apartheid” in South Africa, eradication of diseases, a steady reduction in hunger, development of international law and landmark pacts to protect the environment and planet Earth.

But today, he warned, “climate calamity looms, biodiversity is collapsing, poverty is rising, hatred is spreading, geopolitical tensions are escalating, nuclear weapons remain on hair-trigger alert” and technologies have opened huge new opportunities “but also exposed new threats”.

Mr Guterres has admitted before that the UN’s biggest failing was its inability to prevent medium and small conflicts.

Mr Guterres said the 75th anniversary was an ideal time to realise these aims.

“We face our own 1945 moment,” he said. “We must meet that moment. We must show unity like never before to overcome today’s emergency, get the world moving and working and prospering again.”