While infantry recruits could be trained in a matter of week

Bullet catchers can be corralled in a matter of weeks

An effective infantry will take far longer with far greater resources. Even then, as history has shown, an invading force lined up against indigenous fundamentalism, is sisyphean at the least. If we had a political system that didn't have so much churn and turnover, efforts would have better efficacy in fostering a 'sense of duty' and maintaining a 'pride of ownership,' and that's one major reason we find ourselves in the current state... no one had to fight for what they have... it's all an inherent 'right'