When did the practice of formally “declaring war” cease and why?

Question

Here's a detailed description of ambassador Neville Henderson being received by the foreign ministry in Berlin in 1939. Perhaps the most famous example.

He came in looking very serious, shook hands, but declined my invitation to be seated, remaining solemnly standing in the middle of the room.

'I regret that on the instructions of my Government I have to hand you an ultimatum for the German Government,' he said with deep emotion

This site has a description of Ciano handing out Italy's declarations of war on June 10th 1940:

On 10 June, dressed as a major in the Regia Aeronautica, he handed the Allied ambassadors Italy's declaration of war

When did this formal (slightly awkward) practice of making an official "declaration of war" via an ambassador or foreign minister cease?

It seems as if it stopped in 1945 but am I right? Thinking of the major conflicts initiated by individual sovereign states since WW2, such as Iran-Iraq in the 1980s, China & India, India & Pakistan, the Six Day War, the Falklands, in those examples I am nearly certain there were no formal declarations of war of the kind Neville Henderson or Galeazzo Ciano delivered.

Answer 1

Theoretically, wars are still supposed to be declared. To quote the Hague Convention III of 1907:

The Contracting Powers recognize that hostilities between themselves must not commence without previous and explicit warning, in the form either of a reasoned declaration of war or of an ultimatum with conditional declaration of war.

However, after searching through some sources I have to agree with you - I cannot find any post-WWII war that has been formally declared. The last declaration of war I could find was Soviet Union to Japan in 1945.

Every war that the United States participated in after that was declared as "military engagement" or "police action". United Kingdom behaved similarly, and so did Soviet Union (I don't have a link but Soviet Union always "restored order" or supported a party on its request). I blame the Cold War, none of the sides wanted to admit that they were leading wars of aggression. Same tendency continues however, see for example 2008 South Ossetia War declared as "humanitarian intervention".

Answer 2

There are some exceptions, such as the 2005 Chad declaration of a state of war with Sudan.

Answer 3

In fact formal declaration of war in many countries brings many practical legal consequences, which may include:

• imposition of martial law

• extraordinary powers for the head of state

• ban on political parties and political activities as well as strikes

• limitation of rights of foreign nationals, especially those of the enemy state

These consequences are not often desirable if a war does not affect the general population of the involved party. It is not needed to invest the president with special powers domestically, the enemy nationals living in the attacking state usually either neutral or supportive of the invasion (otherwise why they do not live at home?), the factories do not need criminally prosecute workers who miss workdays to operate normally etc.

The attacked party usually does not declare war because it makes possibility to avoid the full-scale conflict more difficult. Not having declaration of war makes easier for the attacking party to withdraw from the conflict.

Also declaration brings the impression that the war is conducted by a certain power rather than "international community" which is often desirable due to political reasons.

Answer 4

In his judgment in the Tokyo war crimes tribunal, Justice Radhabinod Pal claimed that while in the west there was a convention of declaring war before the resumption of hostilities, the east did not have anything similar. He also provided a number of examples of wars that had been fought without ever declaring war, which is available in the report. So it can be said that even before 1945 the rule was not followed very strictly.