(NewsNation) — The International Court of Justice is being asked to consider South Africa’s case accusing Israel of committing genocide in Gaza.

Israel has rejected the allegations as “atrocious and preposterous,” with Israeli leaders taking the rare step of engaging with the court to defend their international reputation.

Here is what you need to know about the landmark case.

What is the case against Israel?

On Oct. 7, hundreds of Hamas gunmen crossed from the Gaza Strip into Israel, killing about 1,300 people and taking about 240 people hostage.

In response, Israel launched intense military action against Hamas. After 100 days of war, more than 23,000 people, mainly civilians, have been killed in Gaza, according to the Hamas-run Health Ministry.

South Africa’s 84-page filing says Israel’s actions “are genocidal in character because they are intended to bring about the destruction of a substantial part” of the Palestinians in Gaza.

The case refers both to what Israel is actively doing, like conducting air strikes, and for what it is allegedly failing to do, like prevent civilian harm.

South Africa is accusing Israel of:

• Killing or causing serious bodily or mental harm to members of the group
• Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part
• Imposing measures intended to prevent births within the group
• Forcibly transferring children of the group to another group

During opening arguments, South African lawyers said the latest war is part of decades of Israeli oppression of Palestinians.

Israel’s response

Israel’s Foreign Ministry has argued South Africa’s case lacks legal foundation and constitutes a “despicable and contemptuous exploitation” of the court.

“No, South Africa, it is not we who have come to perpetrate genocide, it is Hamas,” Israeli Prime Minister Benjamin Netanyahu said. “It would murder all of us if it could.”

Israel says it is taking a number of measures to prevent civilian casualties, including airdropping flyers that warn of incoming attacks and calling civilians’ phones to urge them to leave targeted buildings.

How is genocide defined?

South Africa asked the ICJ to order Israel to immediately stop the war, alleging it violated the 1948 Convention on the Prevention and Punishment of the Crime of Genocide, which was drawn up in the aftermath of World War II and the Holocaust.

The convention defines genocide as acts such as killings “committed with intent to destroy, in whole or in part, a national, ethnic, racial or religious group.”

Genocide has been historically difficult to prove in international courts. Experts told Axios this is because the legal definition does not give a clear threshold for determining when the listed acts rise to the level of genocide. The definition also relies on intent, which is difficult to prove.

What is the International Court of Justice?

The ICJ is the top court of the United Nations, based in The Hague in the Netherlands.

It was established after World War II to settle disputes between states and give advisory opinions on legal matters, which is what it is being asked to do with Israel.

The Hague calls itself the international city of peace and justice. It is home not only to the ICJ but also to the International Criminal Court. The two courts have different mandates.

Unlike the International Criminal Court, the ICJ cannot prosecute for crimes of the utmost severity, like genocide. However, its opinions carry weight with the U.N. and other international institutions.

What happens next

The ICJ could rule quickly on South Africa’s call for Israel to suspend its military campaign, but a final ruling on whether Israel is committing genocide could take several years.

South Africa’s filing includes a request for the court to urgently issue legally binding interim orders for Israel to “immediately suspend its military operations in and against Gaza.”

If the ICJ rules in their favor, it would, in theory, protect Palestinians from what might ultimately be declared genocide.

The 15-member U.N. Security Council is the organization’s most powerful body, charged with maintaining international peace and stability.

Its tools range from sanctions to authorizing military action, but all actions require support from at least nine council nations and no veto by a permanent member — the United States, Russia, China, Britain and France.