This task involves creating answers to complex questions, from a given passage. Answering these questions, typically involve understanding multiple sentences. Make sure that your answer has the same type as the "answer type" mentioned in input. The provided "answer type" can be of any of the following types: "span", "date", "number". A "span" answer is a continuous phrase taken directly from the passage or question. You can directly copy-paste the text from the passage or the question for span type answers. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words. A "number" type answer can include a digit specifying an actual value. For "date" type answers, use DD MM YYYY format e.g. 11 Jan 1992. If full date is not available in the passage you can write partial date such as 1992 or Jan 1992. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words.

Passage: Col. Edwin Sumner conducted a campaign against the Navajo in 1851. He delegated Maj. Electus Backus to build Fort Defiance in the middle of Dine bikeyah . Col Sumner entered Canyon de Chelly but Navajo harassment attacks caused him to withdraw. In 1855 a treaty was signed at Laguna Negra by Manuelito and Zarcillos Largos for the Navajo and Henry L. Dodge , Governor Merriweather, and General John Garland. Two years later a severe drought hit the Navajo and decimated their livestock and agricultural resources, causing a famine in the winter of 1857-1858. A time of social disruption ensued. Surrounding tribes gradually increased their attacks on the weakened Navajo. The Navajo demanded in 1858 that Fort Defiance stop grazing their livestock on prime Navajo land. Soldiers shot 48 cattle and 8 horses belonging to Manuelito. Navajo warriors killed a servant of the commanding officer in retaliation for the killing of their people's livestock without compensation. The United States military demanded the murderer be brought to them, or they would begin a war. The Miles Campaign was sent against them, leaving Fort Defiance on September 9.
Question: How many years after Col. Summer conducted a campaign against the Navajo was a peace treaty signed?
Answer type: Number
4.