I'm afraid that this comment is not the pinnacle of intelligence that you think it is. But for people who come by and want to know why this dark matter suggestion is fundamentally ill-informed and wrong:

Dark matter isn't merely "not bright" matter, it is matter which does not interact with electromagnetic radiation. It is generally expected that the vast majority is non-baryonic, for a variety of reasons.

The observed density of all matter in the universe is about 30% of the universe's critical density, but Big Bang nucleosynthesis results readable in the cosmic microwave background show much less helium and lithium than you would expect if it were baryonic — it is safe to say that baryonic matter is only 5% of the critical density. Moreover, small dense objects (black holes) would produce gravitational micro-lensing effects which aren't present, while more diffuse objects would affect the absorption spectra of light.

And finally, the observed distribution of dark matter in the universe just ... sorta makes it a rather poor candidate for war debris.