"At present, indeed, they were well supplied both with news and happiness by the recent arrival of a militia regiment in the neighbourhood." (pg. 29)
The militia referred to here is a group of volunteer troops for homeland security against an anticipated Napoleonic invasion. Yet another cultural context clue added in by Austen to give the novel a sense of realism, the arrival of the militia also gives the Bennet daughters the chance to be taken in by Wickham and for Liz to continue to be mislead about Darcy.
Source: Pride and Prejudice Endnotes by Carol Howard