“And if their attack is real, and destroys us?” the Army Chief sneered.

She didn’t take her eyes off the President. “Then if you still decide that a counter-attack is appropriate, the combined strength of our deployed nuclear submarine fleet and remaining domestic silos is still enough to destroy both China and Russia.”

“Damn you,” the President muttered under his breath. Damn her, he thought, for sowing this seed of doubt. Counter-attack was justifiable, he knew that, but only with enough evidence on their side to make it clear-cut. “When will we have visual confirmation of the ICBMs launched against us?”

“No sooner than five minutes, Mr President,” she replied. It was simple maths: they couldn’t confirm that the next wave of attack against them was real until their own counter attack was three minutes beyond the point of no return. In effect, the President had launched his nuclear weapons too soon, and based on too little evidence.

“General,” he said addressing his Army Chief of Staff, “can you confirm we will still be in a position to launch a counter offensive should the weapons we believe to have been fired against us prove to be real?” He stared his aide in the eyes as he addressed the Chief of Staff, and she stared right back.

There was a pause, followed by a frustrated intake of breath from the Chief of Staff. “Mr President, that scenario is not my recommendation. We will have a reduced capability to respond.”

“Is reduced still enough?”

“Yes,” the General eventually conceded.

“Then cancel our attack,” he replied.

“Sir, I must insist that –”

“General, your orders are to stop the attack, now!” the President barked.

Reluctantly, the General returned to his computer and tapped in the command sequence. Looking up briefly at the President and his aide, he shook his head in disgust.

They then both entered the codes that would destroy their counter-attack in mid-air.

The SDN received the command from Air Force One.

A loop in the security protocol detected that this command had initiated a previously unused, new, function.

The SDN was intelligent enough to know this function was new. It had been received during the latest update, which it had accepted. But it hadn’t yet been tested or proven. That wasn’t so unusual; as an advanced defence system, many of the SDN’s commands and events had yet to be exercised for real.

Basic logic tests confirmed the validity of the commands, and ensured that the parameters received did not exceed the specified data types. A simulation of the function call was tried, and completed with success.

The SDN was an array of independent devices positioned in Geostationary orbit above the United States of America. Covertly, of course, some dozen or so other satellites in lower non-geostationary orbits were also part of the SDN, allowing for surveillance of other parts of the world to be linked in to the defence network.

Each independent satellite’s processing and memory contributed to the network’s ‘brain’, which could be thought of as self-aware insofar as it knew of its own component parts, what it was designed to do, and had an understanding of the importance of that role in the defence of the United States of America, which to it was simply a geographical location that contained a number of potential military and civilian targets.

The SDN’s brain had proven the validity of the command it had received. It did not understand the logic of the command, as it was not part of the brain’s known scenarios. But human logic was still tantalisingly out of its reach, as for all its intelligence it was still simply a machine.

Taking its attention away for a nanosecond from the highly classified simulation exercise it was still running, the brain executed the strange new function.

“In an effort to achieve peaceful resolution of the current situation, we have issued the command to destroy our counter-attack until the nature of the threat to the United States of America is more clear.”

The President addressed the video wall. His aide stood nervously behind him. She had made a potentially dangerous enemy in the Chief of Staff, who stood threateningly behind her left shoulder.

The video wall was split between the Russian and Chinese leaders.

“We are still tracking your missiles.” The Russian President didn’t try to hide his anger. “You must recall them now.”

“A delay in your satellite feed, surely,” the President’s voice wavered.

“You bluff!” cried the Chinese head of state. “You seek to destroy us and avoid us destroying you!”

The President turned to his aide. “Can you confirm our offensive has been recalled?” he asked.

She stooped over the computer screen on the desk and tapped a few commands. The results popped up. She typed the commands in again and the same result returned.

“The command was received and confirmed. However,” she swallowed hard, not knowing where to look, “our offensive has not been recalled. It’s too late to recall them now.”

“Mr President,” the Chinese President said with disdain, “Your acts of unprovoked aggression towards the People’s Democratic Republic of China and our friend and ally Russia have left me with little choice but to launch full counter offensives against the United States of America before we are left completely defenceless.”

The video wall blanked out, and a stunned silence fell on the office.

“So what command did you actually send?” The President turned on the Chief of Staff.

“The command to self-destruct all of our missiles,” he said defensively. “I cannot understand why the command failed, when we can clearly see it was received and confirmed by the SDN.”

“Unless NASA is right,” the aide said slowly. She turned the screen towards the men, showing the Russian and Chinese weapons finally reaching their targets around the United States. Seconds after each one hit, the live text feed below updated: RUS010:Negative Impact... RUS018:Negative Impact... RUS006:Negative Impact...

One by one, the weapons reached their targets. One by one, the ground reports confirmed that no impact had occurred.

“The SDN was compromised.” She let the fact sink in. “Our attack on Russia and China has not been recalled, and therefore we can probably expect a real attack from them to reach us in the next half hour.”

The Army Chief of Staff looked at her screen and double checked on his own. His silence confirmed what she had said.

“So, we have been deliberately provided with false information by our own defence systems, on top of the real nukes that blew up this afternoon. Whoever planned this knew we would possibly try to recall our own weapons, so made sure that wouldn’t work,” the President said, astonished.

“God help us,” the aide whispered.

Air Force One’s alarm system broke the long silence that followed. The Captain’s stern voice came over the speakers in the office.

“Get the President to the evac’ pods, we are under attack!”

Guards ran in to the office and bundled the President down a staircase that had opened up in the floor, leaving the Joint Chiefs and the aide above. Moments later, through the small window, they saw the starboard engine of the aircraft explode, severing the wing a third of the way along its length.

The plane lurched to the right, inexorably falling into a downwards spiral in slow motion as the pilots valiantly battled with the one-and-a-third remaining wings to keep Air Force One as steady as possible while the President was evacuated.

“Laser!” the Army Chief of Staff shouted. “The SDN has a built-in network of lasers designed to bring down ICBMs. Only they’re not as effective as we hoped – the power draw is too great and ICBMs move too quickly. We, on the other hand, are an easy target.”