The Instruments of War

The Instruments of War was the ninth episode of series 8 of Doctor Who. It featured the Twelfth Doctor, Clara and the Sontarans.

Plot
In the desert, several camel riders watch a plane crashing using advanced binoculars. One orders the others to activate "the device".

In the TARDIS, Clara is eagerly awaiting her arrival at the Frost Fair of 1641, having decided to go and see for herself because some of her students are doing a project on the subject. The Doctor is a bit grumpy about going at Christmas, considering how long he lived in the town, as well as some odd readings on the TARDIS console, and isn't cheered up by Clara referring to his being carried around in her handbag a week earlier. Unfortunately, the TARDIS arrives in sand, not snow, with no buildings in sight — it's the Sahara Desert. While looking for someone to ask directions from Clara spots a tank, which the Doctor identifies as a Matilda model, used by Allied forces during World War Two - it seems they're in 1941, not 1641. The tank, unfortunately, turns out to be a German tank, which takes them prisoner.

In German Headquarters, Field Marshal Rommel is arguing with Oberst Bruckner about orders to use saturation bombing against the Allies, despite his troops having settled into winter quarters with established supply routes. They are interrupted by "Doctor Johan Schmidt and his assistant Fraulein Oswald" from Berlin, but Rommel is able to see through the psychic paper that got them to him. It turns out that the Germans' Tuareg allies have reported "new friends from the sky", making the Doctor realise that the TARDIS brought them here for a reason. He arranges to go with Rommel to meet the Tuareg, whilst Clara stays behind to snoop around. She quickly strikes up a friendship with the young Unteroffizier Hans Engel, who turns out to have been a cellist in civilian life, but they are interrupted by an equally nosy Bruckner, unconvinced of "Fraulein Oswald's" credentials.

The Doctor and Rommel head to the rendezvous, with the Time Lord sadly remembers all the wars he's been involved in, and that he always tries to find another way out where everyone lives. When Rommel says that how they comport themselves at death is the measure of a man, the Doctor refers obliquely to the Field Marshal's own death in 1944. When they do find the Tuareg, they are using energy weapons; the Doctor promptly uses his sonic screwdriver to cause a light-show that impresses the tribesmen rather than hurts them and demands to be taken to their chieftain.

Back at German HQ, Bruckner orders Engel to prepare a rescue party to "save" Rommel from the Doctor, but also quietly tells Clara that he knows she's not a spy despite her 1641 gown "because I am"...

At the Tuareg camp, their chieftain, Bhaki, welcomes the Doctor and Rommel and happily agrees to introduce them to the men from the stars. The Doctor becomes visibly concerned after recognising the weapon in the tent, proclaiming "This is bad, this is very very bad...", and with good reason: the visitors are Sontarans, led by Kygon Brox of the Eighth Sontaran Battle Fleet.

Bruckner orders Engel to bring "Fraulein" to the grief; Engel fails to believe that Clara is innocent. That said, Engel and Clara are heading towards the Doctor, giving Clara some hope.

Back at the Tuareg camp, the Doctor urges Rommel and the Sontarans not to fight; after all, they have a good amount in common, and there is little cause for battle. Brox, however, is interested in something else - the Doctor. Recognising the time traveller as nonhuman, Brox assumes the Doctor to be an enemy searching for the Warsong.

Clara admits to Engel that she is not German, but also maintains that she isn't a spy. After she explains Bruckner's unfaithful intentions, Engel concludes that Clara cannot be a spy after all — a spy would not say such a ridiculous, implausible thing.

The Sontarans, still convinced that the Doctor is in search of the Warsong, order him to say what he knows, eventually using a mind scythe to get the information out. Bhaki, having seen men "reduced to a husk" with the device, concludes that the Doctor is beyond help...

Engel notices that Bruckner is not going in the direction of the Tuareg encampment. Bruckner orders his driver to halt at this point; he and his soldiers unload their crates of wooden planks, building a structure. Back with the Sontarans, the Doctor is showing Brox "holiday snaps" of past adventures, before explaining that the mind scythe can in fact go both ways. He proceeds to probe the mind of a shocked Brox.

While Engel is incredulous of Clara's claim to be a time traveller, Bruckner sees the notion as perfectly plausible; in fact, her revelation has resolved a conflict he had been working on for a good amount of time. He then confesses that he is indeed a spy — but not a British one...

Using the mind scythe, the Doctor discovers that the Warsong Brox was referring to is a "world engine" that changes the course of war. Despite creating the weapon, the Sontarans struggled to deploy it, so they took it to a primitive world. The weapon lay dormant on Earth for years, only activating when it sensed aggressive technology; however, once Earth reached a level of technological advancement that could be viewed as threatening, the Warsong began to awaken. Hearing the weapon's "overture", Brox's battle fleet came to Earth; however, its signal is not yet strong enough to be fully utilised, so the Sontarans can currently do nothing but try to stop the enemy that seeks it. After convincing Brox that both himself and Rommel can be useful to the Sontarans' goal, the Doctor uses his sonic screwdriver to destroy the mind probe.

Meanwhile, Engel attempts to relieve Bruckner from his command; however, after acknowledging Engel's less-than-satisfactory life, the spy shoots Engel with bolts of green energy. Back at the Tuareg camp, the Doctor and Rommel discuss Bruckner's recent behaviour. The Doctor suggests that his depletion of forces and resources may mean he is wishing to do something more than win the war — more specifically, something involving the Warsong. What's more, the Doctor believes that Bruckner may not be who — or what — everyone thinks he is...

Bruckner uses the Warsong to kill all of his soldiers who are at the location. He explains that the TARDIS' energy is what powered the weapon enough to do so, and that she has helped him satisfy his people: the Rutans.

From a distance, the Doctor and the Sontarans see the Warsong's energy. Brox explains that the weapon's description of "world engine" is quite literal: it will take the energy from people, buildings, and natural formations to turn the entire planet into a weapon...

Seeing that Bruckner has Clara, the Doctor decides to save her, despite the extreme danger. Brox initially dismisses his action as reckless, but the Doctor insists that he is in fact thinking hard: they could pool their resources and seize the not-yet-fully-formed Warsong, for the glory of Sontar. Rommel protests, but the Doctor insists that being on the winning side would be preferable to defeat, regardless of innocent lives taken. However, while out of Brox's hearing range, the Doctor explains that he was merely telling the Sontaran what he wanted to hear.

Bruckner teaches Clara of the Warsong, explaining that the dead soldiers as well as the surrounding sand were used to power it, with the rest of the planet to soon follow.

The Doctor, meanwhile, suggests that the machine may be vulnerable whilst it is still growing. Launching as much as they can at it, at as great a speed as possible, might result in "a lucky break" in the weapon's defences - seemingly their only hope for victory. The Doctor phones Winston Churchill, ensuring that the Allies attack from the other side at the same time as the Axis.

Initially, the Warsong simply destroys the attacking vehicles with ease. However, using his sonic screwdriver, the Doctor changes the harmonic resonances of a tank. As the Warsong's technology is based on sound, the tank is now able to attack the weapon, as well as enter it.

Bruckner suggests that Rommel join him, but the German refuses to take part in the destruction of every human being on Earth. Whilst the Doctor distracts Bruckner, Brox manages to enter the Warsong as well, giving the Time Lord an osmic projector. Bruckner grabs Clara and holds her at gunpoint to stop the Doctor from sending him back in time; however, instead of sending him back in time, the Doctor uses the projector on his gun. Rommel proceeds to push Bruckner off the safe platform they are standing on, into the energy conversion part of the Warsong.

Brox announces the weapon as Sontaran property, but the Doctor reveals his true intentions. However, the Sontaran is severely weakened at this point, and he perishes before he can do anything to the Doctor. The Doctor uses his sonic screwdriver once again, this time destroying the sound-based Warsong. As everyone escapes, the machine explodes.

The Doctor notes the irony of the culturally-bereft Sontarans creating something as lyrical as the Warsong. He suggests that this artistic side of their nature has been bred out, explaining their inability to recreate the weapon. He also assures Rommel that this entire event will be forgotten by the collective of humanity, which will focus instead on finishing World War II.

After this conversation, the Doctor and Clara finally make it to the Frost Fair of 1641. They discuss Rommel, who eventually joined the Valkyrie conspiracy to remove Hitler from rule. After this was discovered, he was given two options: either he would commit suicide and his family would survive, or he would stay alive and his family would be killed. As he chose the former option, this man of war ended up dying for love; and, as the Doctor states, "There are worse things to die for."

Characters

 * Twelfth Doctor
 * Clara Oswald
 * Heinz Bruckner
 * Field Marshall Erwin Rommel
 * General Field Marshall Albert Kesselring
 * Hans Engel
 * Bruno Walter
 * Hermann Abendroth
 * Bhaki
 * Kygon Brox

Continuity

 * Clara teases the Doctor about being carried in her handbag next to her hairbrush and keys "last week". (Flatline)
 * The Doctor refers to his lengthy residence in Christmas. (The Time of The Doctor)
 * The Doctor uses a German version of his regular alias John Smith, "Johan Schmidt". (Exodus; Storm Warning, Mary's Story)
 * The "holiday snaps" the Doctor shows Kygon Brox whilst his mind is linked to Brox's mind scythe include a dinosaur near Big Ben, (Deep Breath) a Dalek with wires connected to it, (Into the Dalek) the Moon hatching, ( Kill the Moon) the Foretold, ( Mummy on the Orient Express) a robot knight, ( Robot of Sherwood) the Boneless, (Flatline) the Teller ( Time Heist) and the Skovox Blitzer. ([ The Caretaker)
 * Clara previously visited the Sahara Desert in the company of the Eleventh Doctor. (Sandblasted)
 * The Doctor has made numerous visits to frost fairs. ( A Good Man Goes to War, et al) Clara and the Doctor do manage to attend a late-19th century frost fair in Silhouette.