simple farmer

1.a military movement or advance all the way through and beyond an enemy’s front-line defense.

2.an act or instance of removing or surpassing an obstruction or restriction; the overcoming of a stalemate:The president reported a breakthrough in the treaty negotiations.

3.any significant or sudden advance, development, achievement, or increase, as in scientific knowledge or diplomacy, that removes a barrier to progress:The jet engine was a major breakthrough in air transport.

in summary
beyond an enemy’s front-line defense…removing or surpassing an obstruction…removes a barrier to progress