The history of the Salvation Army is interesting but Meryl does not feel that she needs a piece on it on the family site.  She might look at how different family members have been involved in the work of the SA in the future.

https://www.salvationarmy.org.uk/about-us/international-heritage-centre/virtual-heritage-centre

gives the official, virtual, S A history. There are also Archives in London & Nottingham

 Wikipedia also has some information is

https://en.wikipedia.org/wiki/The_Salvation_Army

In essence it is a Christian Church (operating in a number of different countries) which also does a lot of charitable work e.g. for homeless people and when there are humanitarian crises.  They use military terminology but a Salvation Army Officer is just a Church Minister.  There is no particular ratio of Officers to Salvation Army members.  The aim is just to have an Officer (sometimes 2 if a married couple or 2 single people working together) for each individual Church.  Each individual Church used to be called a Corps but increasingly the word Church seems to be used instead

The Salvation Army Officers do not stay at any particular Church indefinitely.  They used to get moved round really frequently, sometimes just after 2 years.  However, stays are now longer - due to the problems of schooling

Music plays a big part in Salvation Army worship.  Most Corps have a Band and a Songster brigade (choir) who take part in the services: thus a more joyful form of worship than other Churches. It is less formal and there is no Holy Communion.  Salvation Army Bands play Carols in shopping centres at Christmas and sometimes at other events.  There used to be something called an Open Air which was an outdoor service in local streets before the Sunday morning and evening services which would include the Band.  I don't think this happens any more apart from in some seaside places on the seafront.