Harmar and St.Clair were both fair officers, and in open country were able to acquit themselves respectably in the face of civilized foes.

But they did not have the peculiar genius necessary to the successful Indian fighter, and they never learned how to carry on a campaign in the woods.
They had the justifiable distrust of the militia felt by all the officers of the Continental Army.

In the long campaigns waged against Howe, Clinton, and Cornwallis they had learned the immense superiority of the Continental troops to the local militia.

They knew that the Revolution would have failed had it not been for the continental troops.
They knew also, by the bitter experience common to all officers who had been through the war, that, though the militia might on occasion do well, yet they could never be trusted; they were certain to desert or grow sulky and mutinous if exposed to the fatigue and hardship of a long campaign, while in a pitched battle in the open they never fought as stubbornly as the regulars, and often would not fight at all.
The Regulars in Indian Warfare.
All this was true; yet the officers of the regular army failed to understand that it did not imply the capacity of the regular troops to fight savages on their own ground.

They showed little real comprehension of the extraordinary difficulty of such warfare against such foes, and of the reasons which made it so hazardous.