Twenty-four years ago, in one of the darkest days of the Bosnian war, over 8,000 Bosniak Muslims were murdered by units of the Serb army.

On Thursday, thousands will remember the victims of the Srebrenica Massacre.

Every year, more victims are laid to rest in the memorial cemetery. This year, there are 33 new graves but around a thousand people are still considered missing.

The following interview with former NATO deputy assistant Secretary, and former NATO spokesperson at the time of the war, Jamie Shea, has been lightly edited for content and clarity.

General Mladic is in jail for life - has there been justice served, in the 24 years following the genocide?

Certainly, the Srebrenica massacre did lead to the first ever international prosecution for the crime of genocide, even though the UN Convention on Genocide has been in existence since 1948. So to that extent, yes it was a significant step forward for international law and the notion of accountability. It was not just General Mladic, it was his deputy General Krstic who was also in command on that day, who was the first person to be convicted for genocide- and of course the political mastermind, Radovan Karadzic has also now finally faced justice. So you can argue that at least in the responsibility to protect an international human rights law and the willingness of the international community to go after these terrible war criminals, this disaster, this catastrophe at Srebrenica, at least had a more positive follow up.

What was your experience, at the time?

Well, as NATO spokesman at the time, I felt a terrible sense that this could and should have been prevented, because it was clear that these so-called UN safe areas where the UN forces were meant to protect civilians, Bosniak civilians trapped inside these cities, that this was not sustainable, and it could lead to a massacre. And my sense was with the NATO aircraft in the region at the time with the UN troops, the international community should have laid down some kind of red line, to the Bosnian Serb forces not to go into these areas, and not to commit the massacres. And some kind of force, even though it was risky, was worth using to prevent this- for example, a few years later NATO did lay down these red lines in Kosovo with a much more rapid intervention, and with a loss of life in Kosovo which is one tenth the number of people who lost their lives in Bosnia. So, in a way it was a failure of prevention and in hindsight, even if maybe some of the deaths could not have been prevented, the international community should have intervened much earlier.

Looking back now, 24 years on, do you see this as the UN's darkest hour?

Well it certainly was. And to his great credit, the late and great UN Secretary General Kofi Annan who was responsible at the time for the former Yugoslavia in the UN, he afterwards published an extremely candid by UN standards, honest report on what had gone wrong- the over-ambitious mandate, the under-resourcing of the missions, though of course it's the nations that provide the troops and not the UN. And that led to significant reforms of UN peacekeeping, which arguably today is making UN peacekeeping in places like Africa better planned, better resourced, better supported by the international community, much more effective. So I think yes the UN, as well as NATO did draw lessons, and as I said the Kosovo campaign four years later although not perfect, at least dramatically reduced the loss of life we'd seen previously in Bosnia.

Listen to the full interview with Jamie Shea in the video above.