The phrase "decisively shape" is correct and usable in written English.
It implies taking a decisive action that will have a major effect. You could use this phrase in any situation where you want to emphasize the impact of an action or decision. For example: "The new policy will decisively shape the future of the company."
As the following examples show, though usually either dismissed as humble helpmeets or complained about as posthumous image-protectors, they can sometimes decisively shape a book or career.
Even if the debate does not decisively shape the result on May 6, it may nevertheless help to boost the number of people who vote.
Indeed, now that the Americans have focused their minds and gathered the resources, they appear to be in a position to decisively shape the battlefield over the course of the next year.
CAIRO — Through elections, protests, government formations and armed struggle, Arab countries in an arc from Libya to the gulf were engaged this past week more than ever in attempts not to simply overthrow leaders, but to decisively shape the orders that follow.
However, where dynamic factor networks decisively shape the environment, flexibility or plasticity is much more important.
His father, who decisively shaped him, had a hair-trigger temper.
Then there's the fascination of the pitch, which decisively shapes the matches played on it.
Taylor's philosophy has been decisively shaped by his political work.
But he was also one of those rare writers who decisively shaped the medium in which they work.
His experiences in the War of the Spanish Succession (1701 14) decisively shaped his future, leading him to realize that the army was his vocation.
An enduring source of the French pride is that their ideas and historical experiences have decisively shaped the values of other nations.
