Mr Foord, who was only elected last month, has been appointed defence spokesman by party leader Ed Davey in his first major reshuffle.
He will take up the role when Parliament returns from its summer recess in September.
Mr Foord, who was in the Army for 10 years before entering politics, said: “I am honoured to speak in Parliament on defence issues and to demand better for our servicemen and women, of whom we can all be proud.
“They do incredible work and deserve our full support, yet Conservative cuts in an era of global instability worries me deeply.
“Liberal Democrats want to see more investment in troop numbers, which have been cut to record lows by this Government.
“Having served as a Major in the Army, I know what effect these cuts may have.
"With Putin continuing his illegal invasion of Ukraine, it is vital the UK continues to do what it can to support the Ukrainian people in their struggle - both in terms of military and civilian aid.
“I feel proud not only to serve the people of Devon, but also my country by speaking up for our brave troops in Parliament.”