Argentina was ruled by a military junta at the time, which fell after the country's defeat in that war.
I don't know about Ecuador and Peru throughout that period, but Egypt has long had only a facade of democracy.
The closest thing to a war between liberal democracies that I know of is the fight over fishing rights between Britain and Iceland some time in the past 20-30 years. Their navies were involved, and one person died.
The first conflict was in 1958-61 (Iceland extended their fishing limits to 12NM), second in 1973, over the 50NM extension, and the third in 1977 when Iceland extended their limit to 200NM, the standard exclusive economic limit. The UK sent their navy in (Iceland does not have a navy) and also used their ocean going tugboats to ram the small Icelandic gun boats.
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