The phrase "asserted forcefully" is correct and usable in written English.
It can be used when describing someone who has stated something with strong conviction or emphasis.
Example: "During the debate, she asserted forcefully that climate change is an urgent issue that requires immediate action."
Alternatives: "stated emphatically" or "declared strongly".
When asked how their respective triumphs affect each other's self-esteem, Mr Dunham asserts forcefully, "A rising tide lifts all boats.
Many observations of cells were made, but apparently none of the observers was able to assert forcefully that cells are the units of biological structure and function.
Although the government of President Mahmoud Ahmadinejad has asserted itself forcefully and demonstrations have more or less ceased, the political rift opened by the election remains.
One senior American official in Baghdad said the idea had been pushed by Dr. Allawi, who has asserted himself forcefully since being selected as prime minister in a process led by the United Nations earlier this month.
The Grammy Awards show, historically, is a place where tradition asserts itself forcefully.
There is a danger, though, if not a likelihood, that the secret police and their corrupt allies in industry, or radical Islamists, will assert themselves forcefully.
Collaged areas of ground-up herbs create the sculptural texture of protean faces that sometimes sink beneath layers of paint, sometimes merge with their surroundings and sometimes assert themselves forcefully.
Re "Bush Planning to See Voters, and to Be Seen" (front page, Sept. 8): It's time for Presidents Gerald R. Ford and Jimmy Carter, as honorary chairmen of the bipartisan Commission on Presidential Debates, to assert themselves forcefully and publicly in favor of maintaining the traditional three-debate format.
China has more forcefully asserted sovereignty over great swathes of the South China Sea.
