Occurrence of Attributes in Original Text

The text related to the cultural heritage 'Tower of London' has mentioned 'Fortification' in the following places:
Occurrence Sentence Text Source
[61] The fortification that would later become known as the Tower of London was built onto the south-east corner of the Roman town walls, using them as prefabricated defences, with the River Thames providing additional protection from the south.
As a result, he was eager to ensure the Tower of London was a formidable fortification; at the same time Henry was an aesthete and wished to make the castle a comfortable place to live.
It was the last major programme of fortification at the castle.
[131] The Second World War also saw the last use of the Tower as a fortification.