On this day in 1994 the Rwandan genocide was unleashed. Extremist members of Rwanda's Hutu majority set about slaughtering Tutsis and moderate Hutus, irrespective of age or gender. More than 800,000 people were killed in 100 days of murder, rape and torture.
I am in Rwanda today to commemorate the genocide, pay respect to the victims and honour the ordinary people of Rwanda for their remarkable efforts to rebuild their country after experiencing unimaginable horrors.
But today we must not only pause and remember the genocide, its victims and survivors; we must also reflect on the lessons of that experience and the international community's responsibility to prevent a repeat of such tragic human suffering.
I will always remember visiting the Genocide Memorial in Kigali last year, and seeing the photographs of innocent children murdered in cold blood, in the most brutal ways conceivable. I looked at those photographs knowing that the world had not done enough to try to save the lives of those children and their families.
The searing experience of the Rwandan genocide and the atrocities committed during the wars in the Balkans shocked the international community and they changed the way we think about conflict, for the better.
The Responsibility to Protect - the doctrine that the international community has to act when a state fails to protect its people from the world's worst crimes - was born. The African Union is today actively preventing and responding to conflict, and UN peacekeepers have greater authority to protect civilians. A stronger system of international justice is working to catch up with war criminals and to try to deter future aggressors.
I am proud that the UK played a central role in establishing the International Criminal Court and in pressing for stronger UN peacekeeping mandates. We are the second largest bilateral donor of humanitarian aid in the world. We have played a crucial role in peace-building in the Philippines and Burma, and provided much needed help to build stability in Lebanon and Libya.
But the international community as a whole can and should do more. The truth is that our ability to prevent conflict is still hampered by a gap between the commitments states have made and the reality of their actions. Today civilians are still being massacred in Syria, the Central African Republic, Sudan and South Sudan.
The fundamental problem is a lack of political will. We have the laws and institutions and capabilities to do more to prevent these horrors. Yet we often fail to use them, fail to appreciate that other countries' fortunes or misfortunes affect us too, fail to understand or to act on the obligation born of our common humanity to protect our fellow human beings elsewhere in the world from horrendous abuses.
The best way to honour the memory of those who died in the Rwandan genocide is to overcome international division and to redouble our efforts to tackle the crises of today and prevent future crises from breaking out.
As an immediate priority, we must do everything we can to alleviate the suffering of the people of Syria. More than a month ago the UN Security Council came together unanimously to demand the Syrian regime allow access to those in urgent need of humanitarian aid and halt brutal attacks on its own civilians, including the barbaric use of barrel bombs.
But humanitarian access is still denied, more than three million people are trapped in hard to reach areas with no access to food, water and medical supplies, and 5,000 civilians are killed every month. The flows of refugees are putting ever greater strain on Syria's neighbours.
All states, particularly Russia and China, must use their leverage with the Assad regime to demand the implementation of the resolution, and all governments should increase their aid contributions as Britain has done. In parallel, the UK and our allies are intensifying our efforts to bring about a political solution in Syria which is the only sustainable way to end the crisis and people's suffering.
We must also strengthen our efforts to prevent the outbreak of conflict in the first instance. The UN Security Council must watch more closely for the early warning signs of conflict and increase its focus on conflict prevention. We must extend the reach of international justice to strengthen its deterrent effect. We must support fragile states, as the United Kingdom has rallied support for Somalia. We must improve respect for human rights and address injustices.
I firmly believe that foreign policy is not only about responding to crises; its goal must be to improve the conditions of humanity.
When the international community unites, as it is uniting behind Britain's Preventing Sexual Violence in Conflict Initiative, this is something it can achieve. The Global Summit I will co-host in London in June this year aims to bring together the 143 countries that have committed to end warzone rape and to galvanise them into action so that this grave crime that has marked so many conflicts and destroyed so many lives can be eradicated once and for all.
The 20th anniversary of the events in Rwanda is a moment to renew the international community's determination to prevent grave atrocities, to strengthen respect for international law, and to intensify our efforts to prevent conflict. It is not enough to remember; we have a responsibility to act.