 McClellan returned to West Point to command his engineering company , which was attached to the academy for the purpose of training cadets in engineering activities . He chafed at the boredom of peacetime garrison service , although he greatly enjoyed the social life . In June 1851 he was ordered to Fort Delaware , a masonry work under construction on an island in the Delaware River , 40 miles ( 64 km ) downriver from Philadelphia . In March 1852 he was ordered to report to Capt. Randolph B. Marcy at Fort Smith , Arkansas , to serve as second @-@ in @-@ command on an expedition to discover the sources of the Red River . By June the expedition reached the source of the north fork of the river and Marcy named a small tributary McClellan 's Creek . Upon their return to civilization on July 28 , they were astonished to find that they had been given up for dead . A sensational story had reached the press that the expedition had been ambushed by 2 @,@ 000 Comanches and killed to the last man . McClellan blamed the story on " a set of scoundrels , who seek to keep up agitation on the frontier in order to get employment from the Govt. in one way or other . " 
