His independent company of Texas Volunteers under the command of Captain Charles A. Seefield was ordered to Port Lavaca on Matagorda Bay as a part of General John E. Wool's Army of the Center, which was slated to invade Mexico.

[7][8] Upon his arrival in California, Connor was involved in a boating accident in the Pacific Ocean while attempting to establish a new settlement near the mouth of the Trinity River.

[9] On May 28, 1853, Connor was called by Harry S. Love to be his lieutenant in the company of California State Rangers with 20 other experienced Mexican–American War veterans.

However, through the efforts of Governor James Duane Doty and Colonel Connor, federal troops were sequestered at Fort Douglas by Washington and the Pacific Theatre commanding general.

Shortly after the signing of the treaties, officers and enlisted men of the California Volunteers stationed at Fort Douglas established the first daily Utah newspaper called The Union Vedette.

Connor provided protection for non-Mormons and those wishing to leave the Church of Jesus Christ of Latter-day Saints during his three years of service in Utah.

Connor engaged in extensive military correspondence, which was published in 1897 under The War of the Rebellion: A Compilation of the Official Records of the Union and Confederate Armies.

In the early 1860s, population pressures in the Washington Territory near the present-day Idaho–Utah border led to conflicts between immigrant settlers and Native Americans.

After an attack on miners with depositions given in Salt Lake City by the survivors, Connor marched his regiment 140 mi over the frozen winter landscape to "deal" with the Indians.

The Shoshone had been supplied by the Mormons and large quantities of wheat and articles of war were captured by Connor's command after the battle at Bear River.

Connor's dispatches are detailed in The War of the Rebellion: A Compilation of the Official Records of the Union and Confederate Armies of the Pacific Theater.

From July to September 1865, he led the punitive Powder River Expedition against Sioux, Cheyenne, and Arapaho Indians who were attacking travelers along the Bozeman Trail and overland mail routes.

[14] On the whole, the expedition was considered "a dismal failure" carried out with "large, ungainly columns filled with troops anxious to get home now that the Civil War was over.

Little was known about the Bear River Massacre or the life and reputation of Patrick Edward Connor in his native County Kerry in Ireland.

[16] This documentary sets out a detailed account of the massacre and Connor's role in the dispossession and killing of first nation Americans in modern-day Utah, Idaho and Colorado.