Obviously it starts within then home. Domestic violence is perhaps a misleading term but it refers to violence towards family members, not that it necessarily happens inside a house.
If an offender physically (or in some cases verbally) attacks their partner in the park, at the supermarket, down the pub, it all constiutes domestic violence.
In the cases we deal with often the perpetrator will be estranged from their partner for one reason or another - perhaps the offender have been sent to jail because of their violent behaviour, but has then made threats that upon release from prison they will injure or even kill their partners and or children. (Raul Mote did that)
In some cases the victim has fled the family home but their whereabouts have been found out by the enraged perpetrator.
Victims homes are generally an easy target - clearly that is where you can almost guarantee the victim will be at certain times during the day. Hence why target hardening and protection is implemented, so that if the ex partner does show up, the victim can be kept in relative safety, giving them time to call the police, and await till help arrives.
Some victims are advised to move out of the area, to a new undisclosed location, but its not always that easy to just up sticks and go elsewhere.