The mobilisation of the working classes in wars over the last 130 years has often been intimately related to the extension of democratic rights. German voting rights were tied to military service (I think) since the late nineteenth century. Many Jews were enthusiastic soldiers in Kaiser Wilhelm's army - and the struggle to strip these old soldiers of their associated rights and privileges was a defining moment in the growth of fascism. After the first world war, there were extensions of voting rights in Germany and Britain (the suffragettes sealed their agreement with Lloyd George by rallying to the war cause in the 'white feather' campaign).
Again popular participation in the Second World War seemed to accelerate the pace of social reforms, such as the GI bills granting further education and housing assistance in the US, the foundation of the NHS in the UK. Also, Eisenhower's desegregation of the army executive order was a spur to the civil rights movement.
Compulsory military service was a double edged sword. It put more people under military discipline, training them to accept orders. But it also had the effect of giving those same people a greater stake in society, and greater confidence in their power to change things.