"the decisive role" is a correct and usable phrase in written English.
It can be used to refer to a key or crucial role in a particular situation or decision. Example: "The political party's manifesto played the decisive role in their success in winning the election."
These are the political forces Nato played the decisive role in bringing to power.
A month later off Midway atoll, carriers again played the decisive role.
It fails to thoroughly analyze the decisive role that the United States played before, during and after the conflict.
In the choice to go to war, the American people played the decisive role, with a clear majority in support.
Indeed, it is the EU, not the UN or NATO, that must now play the decisive role.
The problem, officials say, is that none of Iran's neighbors are willing and able to play the decisive role alongside the United States.
Where the scholars particularly aided them, he and Mr. Minoli said, was in helping the filmmakers focus on the decisive role played by Pontius Pilate Gary Oldmann).
He insisted that conflicts in 1990 and 1991 could have been avoided, bluntly telling Mr. Kucan, "You opted for violence, you personally played the decisive role".
Yet questions about the Siegelman case persist, including about whether Mr. Franklin played the decisive role he says he did, and not just among the former governor's supporters.
The image of the Libyan revolution in 2011 was something of a fabrication in which the decisive role of Nato air power was understated.
Other jurors acknowledged that comments by Mr. Peterson's fourth wife, Stacy Peterson, made before her 2007 disappearance, played the decisive role in convincing them to convict Mr. Peterson.
