This article will discuss the relationship between military service, civil wars, masculinity and marriage in 1860s Colombia. It will do so by means of an analysis of a letter from Petra Vergara de Santander to her husband, Colonel Santiago Fraser of the Colombian army. This letter, recently donated by Vergara’s descendents to the National Museum of Colombia, casts serious aspersions on several aspects of her husband’s masculinity. As it is an important source for the history of domestic life, gender and the foreign-local encounter in Colombia, the letter is transcribed and translated here. The subsequent analysis reads the letter with gender and civil warfare in mind.