Falklands War (1982)

[Vosem]

"Western world" is usually used today in the sense of "developed nations that speak European languages". Thus, the Southern Cone of Latin America probably does count as part of the Western world, but the Quechua-speaking Andean villages I've visited in Peru likely don't. However, "Western world" is a very inexact terminology whose boundaries are very gray. The Falklands War might qualify as the last war between "Western" countries (though if you include all of Latin America as Western, the 1995 Cenepa War was fought between Western countries, and an insurgency in Colombia is ongoing in the present day -- and where "Western" ends and begins in the Balkans is another can of worms, though I think the Slovenian War of Independence in 1991, while maybe not a "purely" Western war, definitely had culturally Catholic Europeans that are hard to characterize as non-Western on both sides of the fighting), but if you don't emphasize countries so much you can include the Troubles in Northern Ireland, which lasted until 1998, or the ETA insurgency in the Basque Country, which lasted until 2011 -- which both involved guerrilla warfare fought inside of unmistakably Western nations long after the end of the Falklands War.

[Vosem]

"Western world" is usually used today in the sense of "developed nations that speak European languages".

That would make Russia, Serbia and Ukraine Western, which they are clearly not. The Orthodox/Catholic boundary is important.

Russia, Serbia, and Ukraine, are not necessarily "developed nations": https://en.wikipedia.org/wiki/Human_Development_Index#/media/File:2014_UN_Human_Development_Report_Quartiles.svg

The Catholic/Orthodox boundary is important, but it doesn't tell the whole story: I think most would definitely consider Greece to be a "Western" country, even though it is overwhelmingly Orthodox.

I think it is more interesting to look at how Brits and Argentinians viewed each other in 1983 than some abstract definition of Westernness - and then realize that the concept is viewed differently in different parts of the area settled by Europeans.

Fair enough