It was during the test flight of a new generation deep space explorer, the IIE Celeste, the crew of which I was a member of, when it happened.

It was intended that we perform a mere orbit of our home world, Omicron Prime, when we unexpectedly experienced a freak phenomenon known as a "temporal ripple". Time and space distorted, and where once both were linear, they became intertwined and chaotic.

It was through this means that our vessel was sent back into a historical period of our world little known of since the nuclear burnings of 1702 LC - a time of Middle Age culture, where kings still ruled in the commonwealth of the Corianth Empire, on the larger continent.

Despite the opportunities for learning, our captain and the majority of crew insisted that we attempt to return to our own time, using exact measured vectors previously experienced. For a temporal ripple does not simply affect one part of time, but the whole of time within that original space, lasting anywhere from fractions of a second, to a multitude of days, before fading again.

We therefore attempted to return to our original time frame by mimicking the prior conditions of our entry into it.

We almost succeeded.

We appeared in the correct space, and only seven months after our initial disappearance.

And when we did so we saw our world on fire.

Surface scans showed an unknown race of beings, so breathtaking in form as to be as like angels, destroying our world in a true final apocalypse.

There was panic on everything - even our outermost colonies simultaneously claimed themselves under similar attack, and all communications were filled with screaming that preceded abrupt silence.

Space itself was lit up with innumerous craft, mainly civilian, fleeing low orbit of our blazing world - and all of which were being utterly destroyed by unknown vessels.

We almost collided with one - a future flight of the IIE Celeste.

And that is when we hit another wave in the ripple and suddenly returned to our original time frame in space, even almost a second before our first disappearance.

We are the only people known of to have ever travelled into a temporal ripple - and returned alive.

Let me tell you this freely - what we saw of the future was not a possible, nor mere potential future - it was the future.

I have vowed to change that.

Within days an opportunity presented itself - a strange vessel piloted by some being I did not witness, arrived at one of our outposts and claimed to have travelled thousands of years across space and time to visit our own civilisation.

I tested the proof of his claims by equipping myself and then stealing his craft, and inputting the exact same vectors as I could, compensating for the smaller mass with increased velocity, as I steered it into the last remnants of that now fading temporal ripple.

Let me now tell you of one more important thing that I spoke of before - the nuclear burnings of 1702 LC.

They occurred as a result of political conflict between two continents - a democracy versus a republic, both with nuclear capacity and leaders and advisers who should have known better. Their own personal disagreements sent our world into three centuries of dark barbarity.

I am now in a period before that, known only as the Middle Age. Most historical records were destroyed in the mass destruction that occurred in 1702 LC, but of what little we do know is that an empire existed there - the old Corianth Empire - before it became a democracy.

And now for the crux of the matter:

I will attempt to prevent the future destruction of our world, by preventing the nuclear war from ever occurring in the first place - and thus extend our occupancy of space, and the many colonies on other worlds, by centuries. And, not least, our technological capacity to survive and defend ourselves.

I will attempt to change time.

To do this I must destroy the old Corianth Empire, and ensure that it becomes a Republic, and imbue it with similar ideals to the civilisation that once originally destroyed it.

By preventing the nuclear catastrophe, I will avert the future apocalypse and extinction of our species.

Yet to destroy an empire for the better means loss of life - through assassination, and not least the inevitable civil conflict - though with death on a scale far less compared to the atrocities of the future.

And so I pose this question that faces me now:

Who would not kill one man to save a million?

And how many would you have kill to save 25 billion?

I already have mine own answer and have acted upon it.