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: While KSCB was abandoned, the Marines continued to patrol the Khe Sanh plateau, including reoccupying the area with ARVN forces from 5-19 October 1968 with minimal opposition. On 31 December 1968, the 3rd Reconnaissance Battalion was landed west of Khe Sanh to commence Operation Dawson River West, on 2 January 1969 the 9th Marines and 2nd ARVN Regiment were also deployed on the plateau supported by the newly established Fire Support Bases Geiger and Smith; the 3-week operation found no significant PAVN forces or supplies in the Khe Sanh area. From 12 June to 6 July 1969, Task Force Guadalcanal comprising 1/9 Marines, 5th Infantry Regiment (United States) and 2nd and 3rd Battalions, 2nd ARVN Regiment occupied the Khe Sanh area in Operation Utah Mesa. The Marines occupied Hill 950 overlooking the Khe Sanh plateau from 1966 until September 1969 when control was handed to the Army who used the position as a SOG operations and support base until it was overrun by the PAVN in June 1971. The gradual withdrawal of US forces began during 1969 and the adoption of Vietnamization meant that, by 1969, "although limited tactical offensives abounded, US military participation in the war would soon be relegated to a defensive stance.".
Question: How many years did the Army occupy Hill 950?
Answer type: Number
2.