Haller blue army documents from American vice consul in Warsaw

My great grandfather Piotr Kowalski fought in the Blue Army (later known as Haller's Army) during World War I.  He returned via the USS Antigone out of Gdansk on 28 Mar 1920 and arrived in the US on 8 Apr 1920.  On the US Army ship manifest, it states that "All care of American Vice Consul in Warsaw, Poland." It also states that he was part of Polish Army Company "O", but I am 99% sure this is a US designation and not a Polish one.  I want to find out if there is any information in the Vice Consul records about the Blue Army, the units, the personnel, etc.  As of now, I have no idea where my great grandfather fought, what unit he was in, etc.  I am hoping that the Vice Consul documents can shed light on several questions I have about his service.  Thank you.