/ˈmɪlɪteɪt/
[verb] To have a strong influence against something, making it harder to happen or succeed. It is almost always used with the word 'against', as in 'several factors militated against a quick solution'.
A word born from the Roman army that now fights its battles entirely in the world of abstract arguments and ideas.
To understand 'militate', you have to start with the Roman soldier — the miles. This Latin word for a soldier gave rise to the verb militare, meaning 'to serve as a soldier' or 'to perform military service'. The Roman army was one of the most organised and powerful forces the ancient world had ever seen, and the language surrounding it was equally sharp and purposeful. When a Roman militabat, he was not just carrying a sword; he was actively working, serving, striving within a disciplined structure toward a clear objective.
From militare, Latin formed the past participle militatus, and it is from this stem that English directly borrowed 'militate' in the early 17th century. The word entered English writing during a period when educated Europeans were deeply steeped in classical Latin, and writers often reached for Latin-rooted verbs to give their prose a sense of weight and authority. At first, 'militate' carried a fairly close sense of its military ancestor — to serve as a soldier, or to fight on behalf of a cause.
Over time, however, something fascinating happened. The word shed its literal military clothing entirely. By the late 17th and 18th centuries, 'militate' had moved into the realm of ideas and forces rather than armies and battles. Writers began using it to describe abstract factors that 'fought against' an outcome — poor weather militated against the harvest, a bad reputation militated against a man's career. The battlefield became entirely metaphorical, but the sense of an active, opposing force pressing against something remained very much alive.
The overwhelming majority of modern uses pair 'militate' with 'against', and this is where a common confusion arises. Many writers mix up 'militate' with 'mitigate', a completely different word meaning 'to reduce or soften something harmful'. The two look and sound similar, but 'mitigate' comes from Latin mitigare, meaning 'to soften or calm', from mitis (gentle) and agere (to drive or lead). One word pushes hard against something; the other gently takes the edge off. Confusing the two is one of the most frequently noted errors in formal English writing.
The wider family of words descended from Latin miles and militare is large and still very visible in everyday English. Latin miles → Old French militaire → English 'military'; Latin militia (military service) passed almost unchanged into English as 'militia'. Latin militare also gave us 'militant', first as an adjective meaning 'engaged in warfare', and later stretched to describe anyone aggressively active in a cause. Even the word 'mile' shares this ancient root — it comes from Latin mille passuum, meaning 'a thousand paces', the standard unit by which Roman soldiers measured their marches. So in a very real sense, every time you drive a mile, you are counting the footsteps of a Roman legionary.