The phrase "a substantial force of" is correct and usable in written English.
It can be used to describe a significant amount of influence, power, or strength in a particular context, such as in discussions about military, social, or economic matters.
Example: "The organization was able to enact change due to a substantial force of public support behind their initiatives."
Alternatives: "a significant amount of" or "a considerable strength of".
A substantial force of marines -- officers declined to say how many -- are set to move into the Tikrit area within days to root out Iraqi forces in the city, which is on the west bank of the Tigris 100 miles northwest of Baghdad, and has a population of about 100,000.
I pray that some of those words have been a substantial force of change for someone in my audience.
Like their Fatimid predecessors, the Ayyubid rulers of Egypt maintained a substantial force of Mamluk military slaves.
John built up a strong team of engineers for siege warfare and a substantial force of professional crossbowmen.
If a king was able to muster a substantial force of household knights, this would reduce his dependence on the military service of his subjects.
The latter had exploited the power vacuum in the Rhodope, an effective no man's land between the Serbs, Bulgarians and Byzantines, to set himself up as a quasi-independent prince, supported by a substantial force of around 5,000 men.
The emirate of Saruhan offered a more substantial force of 6,000 men in the summer of 1346, but instead of fighting, they plundered Thrace and then defected to join Kantakouzenos' army.
In 1394 95 he led a substantial force there to buttress the position of the English administration.
Opponents and allies President Laurent Kabila of Congo wanted a substantial force that could separate the warring sides.
In the wake of Buddhism's sway during much of the Tang dynasty, Neo-Confucians of the Song and later dynasties explicitly accounted for the reality of the world by positing a generative substantial force, qi (Japanese: ki), capable of assuming a variety of forms: liquid, solid, and ethereal.
Several reconnaissance patrols from the Special Air Service Regiment SASRR) were subsequently inserted in the vicinity of the Courtenay rubber plantation, and later on the other side of Route 2. These patrols were highly successful, detecting the presence of a substantial communist force, while a number of Viet Cong were also killed.
