There are numerous ways of getting defence.
- Local communities could form militias so they could defend themselves.
- Communities could employ mercenaries to defend them. The Vatican City has relied on Swiss guards for hundreds of years.
The civil government is just one method of getting defence and it is not a very good one. Most governments are reluctant to spend money on defence. They also tend to be over ambitious at getting into unnecessary wars, so we should think really careful before saying that we need a government for defence.