During 1938, when Neville Chamberlain announced that the likeliness of a war between Britain and Germany was non-existent, Leon's first worries of war began to arise.
He discussed with Else whether or not to have a child - doubt so clear, in a time of unease and uncertainty about what the future held.
They decided to have a child.
Barnett (Barney) Greenman was born on 17th March 1940.
When Leon's worries began to escalate, he went to the British Consulate. During this visit, Barney officially received his British citizenship, and Leon signed papers which allowed him to leave Rotterdam, for Britain, if war ever broke out.
On Friday 10th May 1940, bombs began to drop on Rotterdam.
Whole communities were flattened; thousands died.
But Leon and the rest of his family managed to survive unscathed.
Leon didn't realise who the attackers were, at first.
But, when he caught sight of the Nazi cross on one of the hovering aeroplanes above, realisation began to sink in.
This was Leon's first encounter with the Nazis.
Four days later, on Tuesday 14th May 1940, the Nazis attacked again. This time with more force, brutality and ferocity.
They gained control.
But Rotterdam - a city founded in 1200 with a population of over 700,000 - was now completely flattened.
After endless worry, Leon finally found his parents after the attack - they were both alive.
A few days after the bombings, Leon walked past his childhood street, Helmerstraat.
It was still burning. Completely destroyed.
The start of Leon's Holocaust truly began when the Nazis started to enforce laws against Jews.
First of all, they were forced to wear yellow stars of David, with 'Jood' (the Dutch word for Jew) branded onto them.
Then, as time went by, more offending - and extreme - measures were put in place.
'Jews not allowed' signs began to appear in shop windows - shops which Leon had strolled freely into, only weeks before.
On the doors of households, there were signs saying 'Jews - no knocking'. In other words, 'Jews - leave at once'.
Then people - Jews specifically - began to go missing.
And they never returned home.
Worrying about his families safety in the future, Leon decided to entrust all of his most important possessions with a non-Jewish friend called Mrs van Nauta.
These items included Else and Leon's £758 life savings, and British passports for Barney, Else and himself.
This was a mistake he would never be able to mend.
The reason behind his actions, was the fear of what the Nazis would do to these items, if they ever went into their possession.
But, in many ways, the Nazis did what he feared, in an indirect way.
Out of fear - about the sanctions of helping a Jewish family - the van Nauta's destroyed all traces of these items.
Now, there was no proof of their British citizenship.
And they were trapped in Rotterdam.