The following text comes from a roadside marker near Canby's Cross that describes the events leading up to General Canby's untimely death:
By April 1873, months of peace talks to end the Modoc War had gone nowhere. General E.R.S. Canby found himself caught between President Grant's Indian Peace Policy and the desire of some settlers to have the Army eliminate the Modoc band. The Modoc leader, Captain Jack, was also caught between peace and war factions. Some Modoc argued that-as in their own tradition-once the leaders of an army were killed, the soldiers would retreat. They pressured Captain Jack to act.
Within minutes of a similar attack at Hospital Rock, eight Modoc attacked the commissioners with hidden weapons. When it was over, General Canby and Reverand Eleazer Thomas were dead, and Indian Agent Alfred Meacham lay seriously wounded. The Peace Policy came to an end.
There's an online brochure from the National Parks Service that gives specifics on the Modoc War that you can read. Wikipedia also gives a good writeup on the life of Edward Canby. There is also another marker next to Canby's Cross that poignantly describes the emotions and fallout from the Modoc War and reads:
Canby Cross ~ Over the years, various individuals and groups have made efforts to memorialize the death of General E.R.S. Canby, the only general to be killed in an Indian War. This wooden cross is a replica of an original erected by a U.S. soldier in 1882, just nine years after the event. Some of the very same troops Canby had commended here in the lava beds were still fighting other Indian Wars, and public interest and emotion about such conflicts ran high.
Although the inscription on the cross may elicit strong emotions in some modern visitors, it illuminates the point that people see events through the lens of their own culture and time. In 1873, what some Modocs considered a justifiable war tactic, the U.S. Army considered murder. No monument commemorates the places where Modocs may have felt their attempts to live peaceably were betrayed.
More than any other Modoc War site, Canby Cross represents the vast gulf between the perceptions of the two sides during wartime, and challenges us to look beyond history to the assumptions of our own cultures. As in all wars, there were no innocent parties in this conflict.
The following excerpts are from a book that the National Park Service has made available
online and detail the incidents surrounding the Attack of General Canby's Peace Commission:
Two days later, the Modocs requested a meeting for April 11. Again the Riddles expressed a fear that such would be dangerous. This time the commissioners listened to the warning. On the morning of the 11th, they met to discuss the situation. Meacham and Dyar argued that the meeting should not be held. General Canby and Doctor Thomas felt otherwise. Canby assured the commissioners that the Modocs would "dare not molest us because his troops commanded the situation." His signal men reported that only five unarmed Modocs could be seen at the tent. Thomas' argument was "that where God called him to go he would go."
Reluctantly, Meacham and Dyar agreed to go along. Eight persons left Gillem's Camp that morning. First on the trail were Canby and Thomas, on foot. Dyar on a gray horse and Meacham on a sorrel rode behind. Then came Frank Riddle, also on foot. Toward the rear rode Bogus Charley and Boston Charley who had spent the previous night at Gillem's Camp, staying with the Riddles at their cave north of the tents. Last of all rode Toby Riddle, sick at heart in her belief that the Modocs would strike that day.
When they reached the peace tent, the whites counted eight Indians including the two Charleys who had ridden with them, all of them armed: Captain Jack, Schonchin John, Ellen's Man, Hooker Jim and Black Jim. This was far different than the six unarmed men promised. General Canby opened the meeting by passing out cigars. Sitting on a rock near a small fire the Indians had built east of the peace tent, Canby opened a conversation with Captain Jack. The tensed commissioners realized that this confrontation was accompanied with danger.
Tens of thousands of words have been written on the events of the next few minutes. One of the first descriptions written by a participant was sorely-wounded Meacham's report to Secretary Delano:
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Gen. Canby assured the Inds. that he was here for the protection of both parties, and to see that the Com.sn faithfully performed their promises. About this time two armed Indians [Barncho and Sloluck] suddenly appeared from the brush in our rear. An explanation was asked and Capt. Jack replyed [sic] by snapping a pistol [a misfire] at Gen. Canby, saying in Indian "all ready" after which Gen. Canby was dispatched by Cap. Jack with a pistol and knife. Dr. Thomas by a pistol shot in the breast and a gun shot in the head by Boston [Charley]. Meacham [and Dyar] attempting to escape toward camp, the former followed by Schonchin John, and the latter by Black Jim and Hooker Jim. Schonchin fired six shots at Meacham, hitting him four times, and leaving him for dead. Boston attempted to scalp him and was deterred by the Modoc woman [Toby Riddle]. Dyar escaped unhurt, although fired at three times by Black Jim who was only a few feet away, and twice by Hooker Jim by whom he was pursued. After running about two hundred yards he turned upon his pursuer with a small pocket durringer [sic], when the Ind. turned and run back — thus letting Dyar get away.
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The tensions of gradual compression (Canby's goal of gradually closing in on the Modocs at the Stronghold) had exploded. The author lay dead. The time was twelve minutes past noon.
The result of the attacks at Hospital Rock and at Canby's Peace Commission would result in a second battle at Captain Jack's Stronghold four days later but would eventually cause the Modocs to recede further south within the Lava Beds. Captain Jack and his remaining men would surrender on June 1, 1873, thus ending the Modoc Indian War.