三十六计 Thirty-Six Stratagems: 借尸还魂 Borrow a corpse to resurrect the soul

借尸还魂 jièshīhuánhún
Borrow a corpse to resurrect the soul

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有用者，不可借；不能用者，求借。借不能用者而用之，匪我求童蒙，童蒙求我。
Take an institution, a technology, a method, or even an ideology that has been forgotten or discarded and appropriate it for your own purpose. Revive something from the past by giving it a new purpose or bring to life old ideas, customs, or traditions and reinterpret them to fit your purposes.
In 234 AD, Shu's military advisor(军师 jūnshī) JhuGe Liang passed away(去世 qùshì) through over-work and illness. Before he died, he knew that once he was gone, the Wei army would take this opportunity to attack Shu. So he instructed the chief of staff Yang Yi to withhold(封锁 fēnɡsuǒ) the news of his death until the Shu army had safely retreated. He even gave detailed instructions on how to defend against an attack during their retreat.

SiMa Yi, the general of Wei, was an expert in astrology(星象 xīnɡxiànɡ), so he knew that his arch rival JhuGe Liang had passed away. But he was concerned that he could be faking his death to lure the Wei army into a trap. So he sent some scouts to find out if there were any movements in the Shu army first. To his surprise, the Shu army had completely retreated. This convinced SiMa Yi that JhuGe Liang had indeed died. So he led his army on a frantic chase. Finally, the Wei army caught up with the Shu army. But when the Wei army charged forward, suddenly they heard a sound of canons. There were several generals who escorted a carriage on which, to his horror, sat JhuGe Liang. SihMa Yi shouted out loud, " We've been tricked!" Immediately, he sounded retreat, and the Wei army retreated to as far as 50 kilometers back. What SiMa Yi did not know at the time was that JhuGe Liang had indeed died earlier. What SiMa Yi saw sitting on the carriage was just a wooden dummy(木偶 mùǒu) dressed up like JhuGe Liang. And all these events were anticipated and planned for before Jhu Ge Liang's death.

In battle, strategies and tactics from recent wars may be expected, but older methods may have been forgotten or assumed to be no longer of value.

In business, plans and strategies which were shelved in the past may now be applicable. Old brands may also be revived, for example car marques of long-deceased companies from the 'golden age of motoring'.

The general principle of reuse is to find what works and ensure the knowledge and learning from this is continued rather than being rejected as 'old stuff'.