A mustang officer, Fontes was commissioned in 1986 and focused on Central Asia, eventually serving in Tajikistan, Pakistan, and India, including a few years in Afghanistan.

She assumed her final position after the resignation of Michael Flynn from the Trump Administration ended her announced role as senior director for India, Pakistan and Central Asian Affairs on the United States National Security Council.

[5] Born in the state of Washington[4] and raised in Kuna, Idaho,[6] Fontes grew up in Treasure Valley and reports that she sought a military career ever since she was 12 years-old.

[9][12] After the September 11 terrorist attacks in 2001, Fontes served at United States Central Command J5 overseeing issues of political-military cooperation in Afghanistan.

[13] In June 2004, she was moved to Combined Forces Command - Afghanistan headquarters in Kabul and served under David Barno as the head of the CJ5 staff for political-military coordination.

Her staff was responsible for keeping General Barno "on message", overseeing the policies impacting military operations, and performing liaison work with both the Afghan Ministry of Defense and United Nations Assistance Mission in Afghanistan.

[14] At the end of her first year in Afghanistan and following Karl Eikenberry's assumption of command from Barno, Fontes volunteered to lead the Provincial Reconstruction Team (PRT) in Tarinkot.

Green said that Fontes, then a lieutenant colonel, pitched in a few hundred dollars of her own money to host a lunch on the PRT for local Afghan leaders.

[17] An article in Vanity Fair relates a story that she once refused to depart a meeting with Afghan elders in Chora District under threat of small arms fire, for fear of appearing weak in the face of the Taliban.

[33] Asked in November 2017 about her assignment, Fontes replied to Stars and Stripes that she hoped the public would judge her performance as an Army officer regardless of her gender.