A modern doctor of Ming history lived in Hongwu for fifteen years. Faced with Zhu Yuanzhang's butcher's knife, he chose to drill ventilation holes for the iron barrel ancestor.
He couldn't stop the Jingnan Campaign, but he could cut off his fingers in the Blue Jade Case and save three thousand craftsmen - these people would make repeating fire guns a hundred years later.
He could not change the Little Ice Age, but he buried sweet potato vines in Fengyang thirty years earlier, which prevented the famine from coming half a year later in the late Ming Dynasty.
They even secretly hid farmland maps on Zhu Di's treasure ship and stuffed benevolent political notes into Zhu Yunwen's fragments - knowing clearly that history will bleed, but wanting to let less blood flow.