Can this refer to a group?
Yes. An older usage of the term refers to a group of soldiers, not a single soldier as we generally understand today.
Originally “a commando” was a type of combat unit, as opposed to an individual in that unit. In other languages, commando and kommando denote a “command”, including the sense of a military or an elite special operations unit.
[…] During World War II, newspaper reports of the deeds of “the commandos” only in the plural led to readers thinking that the singular meant one man rather than one military unit, and this new usage became established.
Why I Looked It Up
I’m reading The Covenant by James Michener which is a fictionalized history of South Africa. In several places, they refer to “a commando” meaning a group of soldiers. Additionally, some characters say they are out “on commando,” refer to a duty or operation.
Interestingly, Wikipedia mentions that the word/usage has significant Dutch/Afrikans origins:
[…] the word stems from the Dutch word kommando, which translates as “a command or order” and also roughly to “mobile infantry regiment”. This term originally referred to regiments of Boer mounted infantry, who fought against the British Army in the First and Second Boer Wars.
It is also possible the word was adopted into Afrikaans from interactions with the Portuguese in their nearby African colonies, in whose language the word comando means “command”. Less likely, it is a High German loan word, which was borrowed from Italian in the 17th century, from the sizable minority of German settlers in the initial European colonization of South Africa.
In the back of the book, I found a glossary that included this:
Commando: Boer military unit (member of such unit)
The definition concedes both the individual and group usage.
Later in The Covenant, the adventures of “the Venloo Commando” are discussed. I went looking for some information on this, and while I’m not sure it was a real thing, there’s an entire Wikipedia entry for Boer Commando, which discusses the exploits of the Boer military units during the Second Boer War in the early 1900s.