The phrase "initially argued that" is correct and usable in written English.
You can use it when you want to introduce someone else's statement or opinion that was offered at the beginning of an argument. For example: "John initially argued that he should continue to stay on the project, but eventually decided to step down."
Ms. Martz initially argued that Grace should clean the site.
Silverstein initially argued that the Lower Manhattan Development Corporation had compensated Libeskind in full.
Prosecutors initially argued that flammable material was thrown into the train.
NJOY initially argued that it had made no health claims and therefore shouldn't be regulated.
He initially argued that Ms. Schapiro was too soft to turn around the agency.
Bush administration officials initially argued that NATO should fill that void, because the American military was overextended in Iraq.
Government lawyers argued that the claim should not be heard, initially arguing that under the legal principle of state succession, the Mau Mau veterans should be suing the Kenyan government and not the British.
Political considerations were what made Mr. Pollack and Mr. Mearsheimer initially argue that the military campaign should have waited till spring 2002 in hope of peeling off Pashtun supporters of the Taliban who might then have been persuaded to create a new government.
We initially argue that Algorithm 1 is correct for update transactions only.
Cochrane initially argues that communtarianism, using British society as an example, can be used to expand justice to animals.
As our results suggest that coordination and strength are important contributors to functional performance in men, one could initially argue that it is necessary to train coordination and muscle strength in men to preserve function and prevent further decline.
