It is a question that we ask ourselves every single day. Whether trivial (what if I had taken a different route to work?) or significant (what if a past relationship had turned out differently?), there is something in the human psyche that loves to explore the possibilities of paths untaken. Taken further, it is an idea that lies behind the film Sliding Doors and which has spawned an enduring interest in alternative history.
The broadcast of popular, big budget alternative history series such as SS-GB and its American cousin The Man in the High Castle have drawn new interest to the genre. What many viewers may not realise is that alternate histories have been intriguing audiences for centuries. The Roman historian Livy, writing around 9 BC, speculated on what might have happened had Alexander the Great had turned west and attacked Rome rather than Persia.
In SS-GB the Germans successfully carried out the real-life invasion plan codenamed 'Operation Sealion'. The possibilities of this plan have always fascinated historians. In 1974 a major wargame was hosted at the Royal Military Academy, Sandhurst, to test whether Operation Sealion would have been successful (it was never implemented in the Second World War due to the British winning the aerial Battle of Britain). Six umpires - three British and three German - all of whom were senior officers in the Second World War, presided over the game. At its conclusion, they were unanimous in their opinion that Operation Sealion was unworkable and, had it ever been launched, it would have ended in a serious defeat for Germany.
In SS-GB, something must have been different: perhaps the Operation Sealion of that reality was altered somehow to make it successful? Perhaps the British made a critical error? In this new reality, it could be that Germans won the Battle of Britain and used the Luftwaffe to devastate the Royal Navy, thereby allowing an unimpeded landing. Or perhaps German forces managed to land on the coast and the British Army, brave but battered after the evacuation at Dunkirk, unexpectedly crumbled.
As well as offering us historians the delicious conundrum of 'How did the Germans make Sealion work?' SS-GB makes us consider what life in an occupied England may have looked like. We know from the real-life examples of occupied Europe that the SS would have worked with existing law enforcement. Scotland Yard would have become a tool of the occupiers. Characters like Archer existed across Nazi-ruled Europe - men and women torn between 'doing their job' for the enemy and supporting resistance movements that promised liberation.
SS-GB also illustrates the incessant infighting that existed in the Nazi hierarchy. The SS and the German Army were competitive and conflicted. This conflict forms the basis of the plot of SS-GB and draws upon the reality of Nazi government. Hitler practised a 'divide and rule' policy with his subordinates to prevent challenges to his position. Individuals created their own powerbases, fought to gain favour, and conspired against one another. The chaotic world of Nazi bureaucracy was encapsulated in SS-GB through the fascinating rivalry of Huth and Kellerman.
SS-GB also explored what a British resistance movement may have looked like. It is easy to imagine heroic resistance fighters lurking behind every wall, but the real-life experience of occupied Europe shows that the resistance was a true underground movement that had its own internal conflicts. In SS-GB the cunning and ruthless resistance leader Colonel Mayhew made for a striking yet realistic counterpoint to the typical image of British officers obsessed with fair play.
For students of history, mapping backwards and working out how history could have changed - if at all - and how the new reality would have looked can be as challenging a mental exercise as working out what really happened!
In these challenging times, "What if" is a question we must keep asking.
Spencer Jones is a Senior Lecturer in War Studies at the University of Wolverhampton and co-editor of Over the Top: Alternate Histories of the First World War.Suggest a correction