"A" or "the" merger of two companies

In January, he was convicted of bribing South Korea’s former president Park Geun-hye to obtain government support for a merger of two Samsung subsidiaries in 2015. The merger was meant to tighten his control over Samsung.

I am curious and wonder about the way a definite or indefinite article is used in cases such as "a merger of two Samsung subsidiaries" in the first sentence above, from a New York Times article. I am very much interested in the logic behind the use of the or a.

Numerous pairs of two could be randomly picked from group firms, but when combining a pair of two subsidiaries--let's call them X and Y--this merger is one unique combination involving X and Y; indeed any randomly selected two could together be considered a unique pair; therefore "the merger of two subsidiaries," X and Y, is more logically natural to me than "a merger."

Could you please point out any fallacy in my logic or explain the reasoning behind the use of the indefinite article a before merger in the quoted sentence?

I guess that this case is similar to "father of two" in terms of whether the or a is used in front of the noun, an article usage question I still could not wrap my head around.

Solution 1:

Your fault in logic is fixing the two subsidiaries as X and Y. In that case, there is only merger possible between X and Y, and the would be appropriate (although a could be appropriate too).

In the passage, the two subsidiaries are not identified: they are merely two subsidiaries. There are many mergers possible between any two subsidiaries, and we're only interested in one (any one) of that set. Which one it is doesn't matter, firstly because the two subsidiaries are not identified, and secondly because it didn't happen anyway. In that case, a is appropriate (although the could be appropriate too).

My secondary cases are because, in the first instance, there could have been more than merger mooted between X and Y, none of which happened; and in the second instance there could have been only one merger between any of the subsidiaries ever mooted.