What does the handshake between the soldier and civilian in this photograph symbolize?

It would be unification.
You forgot to add the attachment. 

“destroyers for bases agreement in the destroyers for bases agreement between the united states and the united kingdom on september 2, 1940, fifty caldwell , wickes, and clemson class us navy destroyers were transferred to the toyalbnavy from the united states navy in exchange for land rights on british possessions.” i hope this you .