In a blog post on Friday, Microsoft president Brad Smith said while the company was aware that technology was creating new ethical and policy issues, "we want the people of this country, and especially the people who serve this country, to know that we at Microsoft have their backs. They will have access to the best technology that we create".
In mid-October, some Microsoft employees sent a letter to management, urging the company not to bid for the contract and saying they had joined the software giant in the expectation that technologies they built would not cause harm or human suffering.
Their letter was sent a few days after Google announced it would pull out of the bidding because it was something that did not sit well with the company.
Smith said Microsoft was founded in the US and had benefitted greatly from what the country offered. " We also recognise that we have a global mission, global customers and a global responsibility. We’ll need to work through these issues in other countries, and we’ll work to do so in an appropriate and thoughtful manner.
"But when it comes to the US military, as a company, Microsoft will be engaged."
He said the debate over the role the tech sector should play in the military had missed two fundamental points.
"First, we believe that the people who defend our country need and deserve our support. And second, to withdraw from this market is to reduce our opportunity to engage in the public debate about how new technologies can best be used in a responsible way," Smith said.
"We are not going to withdraw from the future. In the most positive way possible, we are going to work to help shape it."
In June, Microsoft employees protested against the company's deal with the Immigration and Customs Enforcement in the wake of the agency's separation of migrant children from their parents at the Mexico-US border.
The same month, Amazon employees wrote to their boss, Jeff Bezos, telling him not to sell the company's Rekognition facial recognition software to law enforcement agencies and to cancel a contract for hosting data-mining company Palantir on its cloud.
In May, a dozen Google employees quit the company to protest against its involvement in a Pentagon initiative named Project Maven where Google's AI technology was being used to improve targeting by drones.