Buuxi weedha soo socota: Dib ugu laabashada Congo-Brazzaville, Mondjo wuxuu u adeegay sarkaal ciidan, wuxuuna ahaa Agaasimaha Casharrada iyo Daraasadaha ee Marien Ngouabi Military Academy ee Brazzaville laga bilaabo 1987 ilaa 1993. Wuxuu garab istaagay hogaamiyaha mucaaradka Denis Sassou Nguesso intii lagu jiray
Juun-Oktoobar 1997 dagaal sokeeye; dagaalku wuxuu ku dhammaaday Sassou Nguesso oo dib u soo ceshay awoodda iyo ka saarista Madaxweyne Pascal Lissouba. Bishii Diseembar 1997, Mondjo waxaa loo magacaabay Taliyaha Aagga Milatariga 1, oo ay ku jirtay caasimadda dhaqaalaha ee dalka, Pointe-Noire; wuxuu sii joogay jagadaas muddo shan sano ah. Waxaa loo magacaabay Madaxa Shaqaalaha ee Ciidamada Qalabka Sida ee Congo 20kii Diseembar 2002, waxaana loo dalacsiiyay darajada sarkaal-weyne ("général de division").