"act as peacemaker" - why is there no article?

Question

Source: http://www.bbc.com/news/magazine-27713847

And on Ukraine there's one message - that the violence in Eastern Ukraine is all Kiev's fault, that Ukraine is crawling with Russian hating neo-Nazis and fascists, and that it's the US government which is fuelling the crisis behind the scenes while Russia tries to act as peacemaker.

I asked a native English speaker and he said that it made perfect sense to him as written. Though he was not sure how to explain it. So, I'm asking you guys here, why do you think there is no article in front of peacemaker?

Answer 1

I agree. The indefinite article should be there before the noun peacemaker. But then, it seems that speakers and writers do put noun, though occasionally, without any article when it follows to act as... Also as Nohat says, when the noun is put as 'role', it can go without any article.

Here is another instance from The West Briton:

“I am extremely grateful for the continuing support that I have had. I was quite surprised last year to be offered the job but welcome the opportunity to act as leader.”

Another one from The Sun News

It is from this prism that the news of the engagement of a foreign negotiator identified as Australian cleric, Dr. Stephen Davis, to act as mediator between the Nigerian government and Boko Haram leaders should be viewed.

From the newspaper -The Pittsburgh Gazette Times

Lord Kilmarnock today left London to act as British diplomatic representative in Berlin.

Worth noting that the particular phrase act as peacemaker is found elsewhere as well.

The Washington Times for the sentence...

At the same time, we have recognized our broad responsibilities of U.S. leadership, the leadership required, for example, to help keep the peace where it exists and to act as peacemaker in explosive areas like the Mideast.

And DailyMail for the sentence...

Believe me, it wasn’t. Injured and confined to a watching role on the bench, I was dispatched to act as peacemaker by manager Dave Mackay.

The native speakers might put light on this but to me, act as.... [noun] seems to be practiced by some at times.

Answer 2

As a native speaker, the article I see omitted is not a, but rather the. Using OP's and @MaulikB's provided examples:

...while Russia tries to act as the peacemaker.
I [...] welcome the opportunity to act as the leader.
It is from this prism that the news of the engagement of [...] Dr. Stephen Davis to act as the mediator between the Nigerian government and Boko Haram leaders should be viewed.

It may be useful to think of the <noun> in act as <noun> as a proper noun rather than a common noun:

...while Russia tries to act as Peacemaker.
I [...] welcome the opportunity to act as Leader.
It is from this prism that the news of the engagement of [...] Dr. Stephen Davis to act as Mediator between the Nigerian government and Boko Haram leaders should be viewed.

This example is a bit more straightforward, as here, it is actually the title of a position:

Lord Kilmarnock today left London to act as British diplomatic representative in Berlin.

The omission of an article also lends itself to the emphasis of the implicit idea that the role that one is taking (the <noun> in act as <noun>) is not one easily replaced, if at all.

Answer 3

The English idiom "act as X" is based on a metaphor: the topic of discussion is a play and the noun phrase X is the name of a role in that play. Roles in plays are noun phrases that are often proper nouns, but sometimes are common nouns. Either way they don't usually take an article. Typical common noun roles in plays would be things like "narrator", "spectator", "man #1", characters who are not identified by name. In the sentence in question, the metaphor is that the geopolitical situation with Russia, Ukraine, and United States is a play, and the role that Russia is playing is called "peacemaker"; therefore, "Russia tries to act as peacemaker".