The UK has no agreement with the EU about British participation in the establishment of a 'European Defence Union'.
The Withdrawal Agreement and Political Declaration provide the option, but no obligation, for the UK to continue to contribute to CSDP operations and missions on a voluntary basis, and where of benefit to UK interests. This does not undermine the UK's sovereignty, our command or control of our Armed Forces nor does it oblige us to participate in a 'defence union' or any EU defence initiatives.
The UK will retain full sovereign control over its defence, intelligence services and decision-making after leaving the EU. The UK will also retain control over the deployment of its Armed Forces and their equipment. Any future security partnership negotiated with the EU would reflect this position.
The UK currently has no agreements with the EU on military command and control procedures other than those in the Withdrawal Agreement referring to continued participation in CSDP operations and missions during the Implementation Period. UK personnel remain under UK sovereign command at all times.
The UK does not have any agreements with the EU on British participation in the 'Five Eyes' community. Any future relationship agreement with the EU will not undermine our partnership with the US, Canada, Australia and New Zealand. The intelligence cooperation between these 'Five Eyes' partners is the broadest, deepest and most advanced of any grouping of nations and we are committed to maintaining it.
The UK has not entered into any agreements with the EU to participate in the procurement of military equipment from EU-wide organisations. There are no agreements with the EU about British participation in transfer of nuclear technology licensed to the UK by the US.