International Humanitarian Law (IHL) is the set of international rules and legal instruments that seek to minimise the destructive effects of war and prevent needless suffering.

Enshrined in the Geneva Conventions, it does not concern itself with questions of war's legality, but aims to regulate the way wars are fought once a conflict has started.

Above all, it is designed to provide legal protections on humanitarian grounds for those who are either not taking part in a conflict - such as civilians - or for the most vulnerable people who are no longer fighting (such as the wounded, the sick and prisoners.

Perhaps paradoxically, IHL represents a global attempt to humanise armed conflict.

Particularly since World War Two, the evolution of IHL has been deeply influenced by the development of human rights treaties such as the 1948 Universal Declaration of Human Rights, which have reinforced global consensus that everyone is entitled to basic human rights in both peace and war.

But IHL should not be confused with Human Rights Law, although the two regimes overlap, notably in areas such as the right not to be tortured. Certain human rights, such as the right of assembly, can be legally restricted during times of war. IHL, on the other hand, is - at least theoretically - universally applicable when fighting breaks out.

The reality is, of course, more complicated. In recent decades, the rise in the number of civil wars and ethnic insurgencies has complicated the application of the Geneva Conventions, the bulk of which govern cross-border international armed conflicts.

Although there are articles and protocols that apply to non-international armed conflict, many countries have been hesitant to implement IHL in the context of internal violence.

The U.S.-led "war on terror" has complicated matters even further amid arguments from some quarters that the fight against violent Islamist fundamentalism is an entirely new kind of conflict that simply falls outside the parameters of IHL.

Mankind's attempts to protect individuals from the worst consequences of war can be traced back as far as recorded human history.

African tribal cultures have promoted the protection of women, children and elders since the dawn of time, along with the dignified treatment of prisoners. An ancient Hindu text, the Mahabharata, includes guidelines on compassion for unarmed or injured enemies and prohibits the use of weapons that create needless suffering.

Both the Bible and the Koran speak of respect for one's enemy. And the European medieval knights and Japanese Samurai respected sophisticated codes of conduct during hostilities.

Concerted efforts to codify a universal law of war, as opposed to regulations governing one conflict or one group, began in the 17th century with a treatise on conflicts between nations by Dutch jurist and philosopher Hugo Grotius. "On the Laws of War and Peace", published in 1625, set out theories of when war is just and addressed questions of what rules should govern the conduct of war once it had begun.

The birth of IHL as we know it today followed the publication in 1862 of "A Memory of Solferino", an eye-witness account of the horrific aftermath of a battle between French and Austrian armies in northern Italy three years previously. The author, a Swiss businessman named Henri Dunant, had been travelling in the region and was appalled by the lack of medical care for the wounded soldiers.

His book, which called for the formation of national societies to care for war wounded, led to the creation of the International Committee for the Aid to the Wounded, which later became the International Committee of the Red Cross. That in turn led to a diplomatic conference in Geneva in 1864, which adopted the First Geneva Convention for the Amelioration of the Condition of the Wounded in Armies in the Field.

IHL was born.

Subsequent conventions were added in the years that followed. A second convention addressed the protection of the wounded at sea and the shipwrecked and the third in 1929 dealt with the status and treatment of prisoners of war.

In 1949, another diplomatic conference responded to the horrors of World War Two, revising the first three conventions and adding a fourth, which stated the rights and duties of an occupying power and expanded the protections due to civilians.

But international law has always needed to catch up with the changing nature of modern warfare, and it became apparent in the following decades that further legislation was required.

The years after World War Two saw an increase in the number of wars fought within the borders of single countries, as opposed to cross-border conflicts. The Vietnam War in particular, along with the wars of independence primarily in Africa, made it clear that further protections were needed, especially for civilian populations.

In 1977, two Additional Protocols to the Geneva Conventions were adopted, the first of which reinforced protections for civilians in international armed conflicts, the second in non-international confrontations.

Aside from outlining protections for those considered to be no longer taking part in hostilities, various treaties also specifically prohibit the use of certain weapons and military tactics deemed to cause unnecessary suffering, including:

• The 1972 Biological Weapons Convention
• The 1980 Conventional Weapons Convention and its five protocols
• The 1993 Chemical Weapons Convention
• The 1997 Ottawa Convention on anti-personnel mines.

The International Committee of the Red Cross (ICRC), which acts as the guardian of the Geneva Conventions and promotes awareness of them around the world, also provides humanitarian support in conflict zones.

The International Federation of Red Cross and Red Crescent Societies (IFRC), on the other hand, is the official umbrella body that ties together the 180 national societies in the Red Cross Red Crescent movement. They are primarily concerned with emergency response and training within their own countries.

The ICRC summarises seven fundamental principles of IHL.

• Parties to a conflict must at all times distinguish between the civilian population and combatants in order to spare the civilian population and civilian property. Neither the civilian population as a whole nor individual civilians may be attacked. A civilian is only loosely defined, even in the Geneva Conventions, as someone who's not a combatant.

• Attacks may be made solely against military objectives. People who do not or can no longer take part in the hostilities are entitled to respect for their lives and for their physical and mental integrity. Such people must in all circumstances be protected and treated with humanity, without any unfavourable distinction whatever.

• It is forbidden to kill or wound an adversary who surrenders or who can no longer take part in the fighting.

• Neither the parties to the conflict nor members of their armed forces have an unlimited right to choose methods and means of warfare. It is forbidden to use weapons or methods of warfare that are likely to cause unnecessary losses or excessive suffering.

• The wounded and sick must be collected and cared for by the party to the conflict which has them in its power. Medical personnel and medical establishments, transports and equipment must be spared.

• There are now three distinctive signs indicating that medical persons and objects carrying them must be respected - the Red Cross, Red Crescent or Red Crystal on a white background. AlertNet has an explainer on the symbols, or you can find out more on the ICRC website

• Captured combatants and civilians who find themselves under the authority of the adverse party are entitled to respect for their lives, their dignity, their personal rights and their political, religious and other convictions. They must be protected against all acts of violence or reprisal. They are entitled to exchange news with their families and receive aid. They must enjoy basic judicial guarantees.

The legal precedent for the prosecution of war crimes was set at the Nuremberg trials of Nazi leaders in 1945 and 1946, followed by a similar process for Japanese military commanders in 1948.

Those prosecutions were based largely on Article 147 of the Fourth Geneva Convention, which defines war crimes as: "Wilful killing, torture or inhuman treatment, including... wilfully causing great suffering or serious injury to body or health, unlawful deportation or transfer or unlawful confinement of a protected person, compelling a protected person to serve in the forces of a hostile power, or wilfully depriving a protected person of the rights of fair and regular trial, ...taking of hostages and extensive destruction and appropriation of property, not justified by military necessity and carried out unlawfully and wantonly."

The broader category of crimes against humanity is defined as acts of persecution or any large-scale atrocities against a body of people. Examples include murder, extermination, enslavement, deportation, imprisonment, torture, rape and persecution on political, racial and religious grounds.

The term genocide applies to "acts committed with intent to destroy, in whole or in part, a national ethnic, racial or religious group". These include killing members of the group; 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; and forcibly transferring children of the group to another group.

Even the most cursory glance at the world today tells us that IHL is routinely violated.

Implementation of IHL is first and foremost the responsibility of the countries that sign the conventions. States have an obligation to teach the rules of IHL to their armed forces as well as the general public. They must also prevent violations and punish them if they occur.

Where governments have signally failed to prosecute those guilty of war crimes after mass atrocities, the international community has in recent decades moved to intervene with the establishment of United Nations tribunals.

In May 1993, the U.N. Security Council established the International Criminal Tribunal for Yugoslavia (ICTY) to try those responsible for violations of IHL in the territory of the former Yugoslavia since 1991. The International Criminal Tribunal of Rwanda (ICTR) was created in late 1994 in the northern Tanzanian town of Arusha to prosecute those most responsible for the genocide during which hundreds of thousands of Tutsis and moderate Hutus were murdered.

Most recently, a joint national and international court was set up in 2007 to try those responsible for the mass extermination of Cambodians during the Khmer Rouge's three-year reign of terror in the 1970s. Similar processes are under way in Sierra Leone and East Timor.

Perhaps the most significant attempt to address the apparent impunity of combatants in times of war came in 1998 with the Rome Statute of the International Criminal Court (ICC). The treaty, which gives the court jurisdiction over cases of genocide, crimes against humanity and war crimes, came into force in 2002.

The effective functioning of the court, however, continues to be weakened by the United States' refusal to ratify the statute. Washington argues that its soldiers might be the subject of politically motivated prosecutions, but it has not ruled out cooperation in specific contexts such as Darfur, in western Sudan.

Currently, 139 states have signed the Rome Statute and 105 have ratified it. Countries that have not even signed the treaty include China, India, Pakistan, Indonesia and Turkey.

Those wanted by the court include Joseph Kony, head of the Lord's Resistance Army rebel movement in Uganda. The ICC is also investigating alleged crimes in Darfur, Democratic Republic of Congo and Central African Republic.

The United States has suggested that the Geneva Conventions do not apply to what it calls "the war on terror", particularly with regard to prisoners, who it says do not necessarily qualify for IHL protection as prisoners of war.

Human rights organisations, the ICRC and international lawyers all point to explicit statements in IHL that call for independent tribunals to decide on the status of prisoners. The military tribunals set up by the United States to try cases in Guantanamo Bay are widely viewed as falling short of the required independence.

They also point to the absolute and universal prohibition on torture, which U.S. forces have allegedly flouted, most notoriously in Baghdad's Abu Ghraib prison.

And although there is no clear definition of "terrorism" in IHL, organisations such as the ICRC argue that acts of terrorism in war time are covered in the Geneva Conventions, which forbid indiscriminate violence against civilians.

Under IHL, other acts of "terrorism", such as the Sept. 11, 2001 attacks on New York and Washington, are still subject to both domestic and international law and cannot be placed in a legal vacuum where torture, kidnap and unlawful detention are regarded as permissible.