In The Day of the Doctor, and in Doctor Who more generally, there often seems to be a distinction drawn between two kinds of mindset: that of peaceful exploration, inquiring into the secrets of the universe, and that of violent conquest and destruction.

There's little doubt which of these two sides the Doctor is on. 'I want to see the universe, not rule it,' he tells the Master in Colony in s.p.a.ce (1971). This might explain what the Twelfth Doctor has against soldiers. In Into the Dalek (2014), he won't allow a soldier to join him in the TARDIS:

'I think you're probably nice. Underneath it all,

I think you're kind and you're definitely brave.

I just wish you hadn't been a soldier.'

The Twelfth Doctor, Into the Dalek

In The Caretaker (also 2014), the Doctor is rude to schoolteacher Danny Pink because Danny used to be a soldier. In fact, the Doctor seems unwilling to grasp that Danny might be intelligent or know anything about maths let alone that that is the subject he teaches because of the job he used to do.

It doesn't help that Danny with the best of intentions upsets the Doctor's plan to rid the Earth of a deadly Skovox Blitzer. When Danny suggests they should call the army in to help fight the creature, it seems to confirm the Doctor's worst suspicions that Danny is exactly the sort who, presented with a new problem, starts shooting at it. It's as if the Doctor thinks that there can be no overlap between the two mindsets, that you can't be a soldier and also have an inquiring mind.

This might seem odd because as we saw in Chapter 7 many of the previous Doctors' companions have had military experience of one sort or another. In Mawdryn Undead (1983), we even discover that the Doctor's great friend Brigadier Lethbridge-Stewart retired from UNIT to teach A level maths. On learning this, the Fifth Doctor doesn't comment, but his expression suggests he doesn't think much of the idea. Even so, it's nothing like the contemptuous way that his later incarnation treats poor Danny.

His treatment of Danny might also seem odd because maths and soldiering have long gone hand in hand. The many achievements of the ancient Greek mathematician Archimedes include designing a huge warship, the Syracusia. The Greeks had such a reputation for military technology that it was later claimed Archimedes had invented a 'heat ray' that set fire to invading vessels by using special lenses to focus sunlight on them though modern tests suggest that that is unlikely.

In the Second World War, the efforts of British mathematicians including Alan Turing to break coded German messages led to the invention of the first programmable computer Colossus, designed by engineer Tommy Flowers in 1943. As we'll see in Chapter 13, Turing went on to use what he learnt from codebreaking in the war to transform our ideas about artificial intelligence.

History has shown time and time again that the pressures of war can actually prompt huge leaps in scientific knowledge and technological ability as each side seeks a new advantage or tries not to lose ground to the enemy. We'll discuss shortly how that is directly relevant to the creation of the Daleks in Doctor Who, but how real scientists approach that war work can be revealing.

On 2 August 1939 before the start of the Second World War, though with conflict looking inevitable physicist Albert Einstein sent a letter to US President Roosevelt about some recent scientific discoveries. Although Einstein signed the letter, it had been written for him by Hungarian physicist Le Szilrd, who had been part of the team that made the discoveries. Szilrd with Einstein's permission used Einstein's fame and reputation to get the President's attention.

The letter explained that it was now thought that the element uranium 'may be turned into a new and important source of energy in the immediate future.' It went on that it was also 'conceivable though much less certain that extremely powerful bombs of a new type' might be made using uranium, too. Such a bomb, it said, might be 'carried by boat and exploded in a port [and] destroy the whole port together with some of the surrounding territory.' The letter suggested that the US government might 'find it desirable to' take more active interest in this new area of research and 'to speed up the experimental work' on it.

Up to this point, the letter reads as little more than an outline of facts: this has happened, these might be the consequences, you might like to watch for developments. For all the 'conceivable' possibility of a new kind of bomb, it doesn't seem terribly serious.

But the letter concluded, almost casually, that Germany had stopped sales of uranium from mines it had taken over, and that this could have been related to the fact that the son of a minister in the German government might have known about the scientific discovery, too. The letter didn't spell out what these details about Germany meant but the implication is surely obvious: the fear that the German government might already be developing these new extremely powerful bombs, which would make a sizeable difference in any coming war.

Why didn't Szilrd and Einstein spell out this warning in the letter? Perhaps they were being polite in not telling the US President what to do. Or perhaps this was a more effective way to get him to do what they wanted: presenting the facts to him in such a way that he would come to the desired conclusion himself. The way it was worded, with the polite suggestion that the US government might 'find it desirable' to look into this matter, the President could be forgiven for thinking that its author, the world-famous physicist Einstein, was not influenced by personal feelings. His reputation as a scientist and the 'scientifically' objective way he stated only the facts without offering an opinion helped make the letter much more persuasive.

Whatever the case, Roosevelt eventually heeded the warning and the US government devoted large resources to ensuring that the USA developed the new kind of bomb before Germany could. It took several years, but the Americans succeeded in building the first 'atomic bomb'. The atomic bomb gave them an extraordinary advantage over their enemies in the Second World War. By that point, Germany had surrendered but j.a.pan was still fighting. In August 1945, US planes dropped two atomic bombs on cities in j.a.pan and, just as the letter had predicted, the bombs were extremely powerful it's thought 129,000 j.a.panese people were killed. With no weapons of equivalent power with which to fight back, j.a.pan had little option but to surrender and the Second World War came to an end.

Historians are still divided over whether it was morally right to use such a devastating weapon against civilians, even though less powerful bombs had been dropped on civilian populations throughout the war, and the use of the atomic bomb may have helped to bring the war to a close and thus saved a greater number of other lives. (This is also the dilemma faced by the Doctor in The Day of the Doctor.) But after the Second World War it became known that the 'race' between the USA and Germany to invent the atomic bomb had been nothing of the sort. The Germans had largely given up on the idea, focusing instead on finding new ways to drop conventional, non-atomic bombs on their enemies. Britain and her allies had developed a new technology called radar that could detect incoming German bomber planes from a distance, allowing them to be intercepted and shot down before they reached their targets. The Germans' solution to this problem was to develop long-range and guided rocket systems that were often too fast for their enemies to stop.

That might suggest that the letter sent to the US President, 'objectively' laying out only the scientific facts, had been wrong. Einstein later said that signing the letter was the 'one great mistake' in his life. Szilrd, with a number of other scientists, later helped found the Council for Abolishing War (today the Council for a Liveable World), with the aim of getting rid of the USA's nuclear weapons that is, more powerful versions of the atomic bomb developed after 1945.

Because, though atomic bombs ended the Second World War, their very existence created a new kind of conflict. Now countries in possession of atomic and nuclear weapons had the power to entirely annihilate their enemies but, because their enemies also had the same weapons, they faced the same threat of annihilation themselves. For most of the second half of the twentieth century, the world was caught up in a 'cold' war, a stalemate in which actual fighting rarely occurred but in which there was the constant threat that the tension would ignite into fully heated conflict and mutually a.s.sured destruction.

We can see something of the impact of this constant threat in the Doctor Who made in the 1960s, 1970s and 1980s, while the cold war was going on. Several stories express the fears and anxieties of their time. For example, The Daleks (19631964) is about the survivors of a nuclear war that has ravaged a whole planet; in The Mind of Evil (1971) and Day of the Daleks (1972), Earth in the present day teeters on the brink of global war; in Warriors of the Deep (1984) it seems the cold war will still be being fought in the year 2084. Yet by Cold War (2013), the conflict has become part of history, perhaps as strange and ancient to us now as the ca.s.sette tapes that store Grisenko's pop music in the story.

Just as the Second World War encouraged the invention of the computer and the atomic bomb, the cold war also acted as a spur for scientific advances. For one thing, the countries in possession of atomic and other nuclear weapons now needed ways to drop them on their enemies that is, other countries, often in other continents. As a result, the German scientists who had developed long-range and guided missiles in the Second World War were recruited by their former enemies. Of the more than 1,500 German scientists who went to work in the USA in this way, one is particularly famous.

During the Second World War, German engineer Wernher von Braun developed the V-2 rocket used by the Germans to bomb Britain and its Allies with devastating effect. Not only did V-2 attacks kill some 9,000 people, but it's thought the number of prisoners and slave labourers killed building the rockets might have been even higher. There is still much debate about how much von Braun was involved or could have changed any of this, but the US government seems to have taken the view that the value of his scientific knowledge and experience was of more importance than his role in the war. They put him to work designing new and better rockets, the results of which were used in long-range nuclear missiles. But there was another practical use for von Braun's research: he developed the huge Saturn V rocket that helped land people on the Moon. It has been argued that the race between the USA and USSR to get into Earth orbit and then to the Moon which we discussed in Chapter 2 was as much about developing technologies and bases for long-range missiles as it was about the 'pure' science of exploring s.p.a.ce.

The point is that we cannot easily separate the two mindsets of scientific inquiry and soldiering however much the Doctor might want to. In fact, his greatest enemies, the Daleks, are warmongering scientists, constantly devising new technologies with which to destroy people. In Genesis of the Daleks (1975), we see how the Daleks were created by the scientist Davros during a terrible war. Davros claims that in creating the Daleks he is only trying to save his own people, the Kaleds, from defeat and extinction. However, in the course of the story we see that he is willing to sacrifice anything even his own people to achieve his goals. His elite team of scientists, working in an underground bunker to develop new technologies for the war effort, are a clear reference to the secret research groups set up by the n.a.z.is during the Second World War. For some of the story, Davros's subordinate, Nyder, even wears a medal a.s.sociated with the n.a.z.is the Iron Cross.

At the end of The Day of the Doctor, the War Doctor decides that, yes, he will use the Moment to end the Time War, even though it means the destruction of his own people and all those billions of children. The Tenth and Eleventh Doctors arrive at the last minute not to stop him, but to ensure that he doesn't have to go through with his terrible decision alone. They know exactly what the consequences of using the Moment will be because they have already lived through it. So their endors.e.m.e.nt suggests that the War Doctor is making the rational, logical choice, however awful it might be.

It's Clara who makes them pause, and she does so by making a distinction between two kinds of mindset: a soldier and something else.

'We've got enough warriors. Any old idiot can be a hero.'

'Then what do I do?'

'What you've always done. Be a doctor. You told me the name you chose was a promise. What was the promise?'

'Never cruel or cowardly.'

'Never give up. Never give in.'

Clara Oswald, the Eleventh Doctor, the War Doctor and the Tenth Doctor, The Day of the Doctor

The Doctor chooses not to be a soldier: faced with this impossible problem, he doesn't shoot it, but uses his intelligence to find an ingenious solution. Yet for all this moment of genius saves his people, the Twelfth Doctor still seems haunted by that choice by what he might have done.

That's why this Doctor doesn't like soldiers not because the mindset of the scientist and the soldier are so radically opposed, but because he knows they can overlap, and how easy it was to convince himself 'objectively' that he should wipe out his own people. It's not Danny the ex-soldier that the Doctor is horrified by, but the soldier in himself. Hence him asking Clara in Into the Dalek: 'Am I good man?'

One further question: how did the Time War begin? Russell T Davies, the writer who came up with the idea of the Time War, has suggested that it was the Time Lords who started it when they sent the Doctor back in time to stop the Daleks ever being created in Genesis of the Daleks.

The Time Lord who gives the Doctor this mission says there are good reasons for doing so:

'We foresee a time when they will have destroyed all other life forms and become the dominant creature in the universe ... We'd like you to return to Skaro at a point in time before the Daleks evolved.'

'Do you mean avert their creation?'

'Or affect their genetic development so that they evolve into less aggressive creatures ... Alternatively, if you learn enough about their very beginnings, you might discover some inherent weakness.'

A Time Lord and the Fourth Doctor, Genesis of the Daleks

Although the Doctor agrees to undertake the mission, when it comes to the crucial moment of actually destroying the Daleks for ever, he is unsure he has the moral right to do so. Some things, he says, could be better with the Daleks, arguing, 'Many future worlds will become allies just because of their fear of the Daleks.'

In fact, Davros argues something similar when the Daleks have conquered everyone, he says, then there will be peace. If the Doctor doesn't agree with that line of reasoning, he is at least unsure about wiping out an entire intelligent life form. After all, he says, wouldn't that make him as bad as the Daleks?

We'll talk more about the morality of this moment in Chapter 13, but ultimately the Daleks survive at the end of the story though the Doctor denies that he has failed in his a.s.signment. He admits that the Daleks 'will create havoc and destruction for millions of years', but says that he also knows that 'out of their evil must come something good.'

But is that correct? In Chapter 5, we talked about Day of the Daleks, in which a group of humans travel back from the future to the present day to kill a politician. They think that by doing so they'll change future events and prevent the Daleks conquering Earth in the future. But the Doctor realises that it's the death of the politician that leads to the Dalek conquest.

Isn't that what happens in Genesis of the Daleks, too? Early in the story, we're told that the Daleks' creator, the brilliant scientist Davros, does not believe that there is intelligent life on other planets. No one dares to disagree with Davros about anything, so his seems to be the prevailing view of the people of ancient Skaro. He's created the Daleks to win a war on Skaro, not to go into s.p.a.ce.

But just by meeting Davros, the Doctor and his friends prove to him that there is intelligent life on other worlds. Worse, Davros learns that his Daleks will conquer these alien worlds in the future. Then, at the end of the story, the Daleks make a sinister pledge.

'This is only the beginning. We will prepare. We will grow stronger. When the time is right, we will emerge and take our rightful place as the supreme power of the universe!'

A Dalek, Genesis of the Daleks

If it wasn't for the Doctor, would the Daleks have had that ambition to conquer the universe, rather than just their own world? The Time Lords gave the Doctor his mission because they foresaw the Daleks destroying all other life forms. The paradox is that in trying to stop such a future from happening, it seems the Time Lords inadvertently start the Daleks on that very path.

Perhaps things would have worked out better if the Time Lords, before sending the Doctor on his mission, had known more about the state of scientific knowledge on ancient Skaro. But then our understanding of history can be problematic, too...