Was the ambush against fetterman's company of soldiers justifiable?

Tensions in the region started rising in 1863, when John Bozeman blazed the Bozeman Trail, a new route for emigrants traveling to the Montana gold fields. Bozeman’s trail was of questionable legality since it passed directly through hunting grounds that the government had promised to the Sioux, Cheyenne, and Arapahoe in the Fort Laramie Treaty of 1851. Thus when Colorado militiamen murdered more than two hundred peaceful Cheyenne during the Sand Creek Massacre of 1864, the Indians began to take revenge by attacking whites all across the Plains, including the emigrants traveling the Bozeman Trail. The U. S. government responded by building a series of protective forts along the trail; the largest and most important of these was Fort Phil Kearney, erected in 1866 in north-central Wyoming.