The most technologically challenging aspect of terraforming Mars will be the creation of sufficient oxygen in the atmosphere to support life. While bacteria and other primitive life can survive with no atmosphere, humans require at least 120 millibars while plants need 1. Although Mars has many chemicals which, if heated, would produce oxygen, this task would require inorbidant amounts of energy, about 2200 terrawatts per millibar. This is about the same as the amount of energy required for plants to create oxygen, with the added benefit that plants can procreate. Therefore, the production of oxygen on Mars can be initiated in two phases. In the first part, advanced engineering techniques supplemented by cyanobacteria and primate plants will be used to produce sufficient oxygen for advanced plants to propagate. Assuming three 125 km radius space mirrors are active, such an endeavour would take about 25 years. Alternatively, photosynthetic bacteria could provide 1 millibar oxygen in about a century. Either way, once there is a supply of oxygen, temperate conditions, a carbon dioxide atmosphere, and water in circulation, advanced plants that have been genetically engineered to be efficient and hardy can be released along with bacterial symbiotes. These plants would represent an equivalent oxygen producing power source of about 200TW. This along with 90TW of space reflectors, and 10 TW of surface power, the 120 millibar goal can be reached in about 900 years. Although this time span may seem long, with the invention and employment of new technologies the timeline could be greatly shortened.