Notch the buried part to make room for an underground power cable:

(image: bottom of 4x4 pressure-treated fencepost, with a square notch that goes about halfway through)

Because nobody will ever try to extract the post (or its broken-off bottom), or if they do, they certainly won’t hoist it out by brute force, or if they do use brute force, they certainly won’t damage the power cable, or if they do damage it, well, fireworks are glorious.

Fortunately there was no glory this time, just a lot of sweat.