Withdrawing from alliance last, quitting about the second of August (10)

'withdrawing' is the definition.
The answer and definition can be both related to change as well as being present participle verbs.
Maybe they are linked in a way I don't understand?

'alliance last quitting about the second of august' is the wordplay.
'alliance last' becomes 'e' (I can't justify this - if you can you should give a lot more credence to this answer).
'quitting' becomes 'vacating' (vacating is a kind of quitting).
'about' is an insertion indicator.
'the second of august' becomes 'u' (2nd letter of 'august').
'vacating' enclosing 'u' is 'vacuating'.
'e'+'vacuating'='EVACUATING'

'from' is the link.

Can you help me to learn more?