The European Union (EU) has already granted a delay to Brexit following talks between Prime Minister Theresa May and other leaders in Brussels.
The extension was made after MPs twice overwhelmingly rejected Ms May's Brexit plan.
A date of 29 March was originally when the UK was set to leave the EU but the delay means Brexit could now happen on one of two days.
Should MPs agree to Mrs May's new deal, Britain will leave the EU on 22 May.
But should they reject it, the delay will be shortened to 12 April and the UK will face the option of asking for another extension or leaving the EU without a deal.
But as things stand, what would Brexit mean for defence?
For defence personnel with spouses or partners who are EU nationals...
Spouses and partners with EU citizenship living in Britain are informed they will be able to stay regardless of whether a deal is agreed.
They might also be eligible to be granted settles status in the UK.
For defence personnel working in the EU...
On the issue of British citizens working in the EU, the guide links to a Department for Exiting the EU document that says the Government “is calling on the EU and Member States to uphold their commitments to citizens and to protect the rights of UK nationals in the event of a ‘no deal’ scenario.”
The rights of British and Irish citizens to work and travel freely between the United Kingdom and the Republic of Ireland will remain unchanged, another linked document states.
For defence personnel living in the EU with their pets...
The guide says that in the event of a no deal exit then pets would still be able to travel to EU countries but “the requirements for documents and health checks would differ depending on what category of third country the UK becomes on the day we leave the EU".
For driving in the EU...
If Britain leaves without a deal then the Government says:
“Your driving licence may no longer be valid by itself when driving in the EU.