I spotted that when a war is described in English, the side described as "allies" is nearly always reserved to the side to which the speaker has sympathy. Although technically the word means somebody in alliance, I virtually never seen the word applied to a supposedly bad side even if that side has an alliance of their own.
It seems this sometimes can be used to point a "good" side in a conflict when commenting the news (even if no Western power is directly involved).
I also noticed that regarding WWII some commenters often say "the Allies and the Soviets" or "the Allies decided to make offensive after that of the Soviets" even though technically the USSR was allied with say Britain and the USA. Instances where the Soviets are grouped into "Allies" are rare especially after the fall of the USSR. Does this usage indicate the commenter's anti-Soviet or anti-Communist inclination?
I also once spotted the usage of the word in regards of the Crimean war between Great Britain and the Russian Empire in the 19th century where British allies (i.e. Turks) were called "the allies". Does such usage also indicate that the author is sympathetic to the British and Turkish side?
Another explanation may be that the word can be simply used to refer any side that is allied with the country from which the speaker originates (i.e. UK and/or the USA in most cases for an English speaker) and as such the speaker is most likely support that side and expresses sympathy to it.
Best Answer
Are allies always good guys? In theory, no. In practice, probably yes.
Most of the major wars (World War I, World II and others), involved LARGE groups of "allies" against a few countries that were also "allied." But the latter were widely perceived as the aggressors against the rest of the world, so few people outside these countries had much sympathy for them.
In practice, the large groups of countries tended to win most of these wars, and called each other "allies." Although they were technically "allies," the smaller groups of countries (e.g. Germany, Austria-Hungary, Turkey in World War I, and Germany, Italy and Japan in World War II) were instead regarded as "partners in crime" by most others.
It's largely a judgment passed by the international community, which is why the "allies" are usually considered good guys.