Valid for 50 years, the deals, signed Tuesday by British Prime Minister David Cameron and French President Nicolas Sarkozy in London, are aimed at retaining both countries' military power in times of shrinking defense budgets.
Sarkozy called the cooperation agreement "unprecedented," saying it showed "a level of trust never equaled in our history."
Both powers agreed to launch an Anglo-French joint expeditionary force of around 10,000 troops that could be deployed as soon as next year. They will also conduct joint nuclear weapons tests and promised to share their aircraft carriers.
Sarkozy and Cameron vowed, however, that each country would maintain its nuclear and naval sovereignty.
"Britain and France will be sovereign nations able to deploy our forces independently and in our national interest when we choose to do so," Cameron said.
Neither side will be obliged to dispatch its carrier, a regulation key to avoid awkward diplomatic crises, observers say.
France and Britain have differed before on military operations -- for example in the Falklands and in Iraq -- and teaming up militarily doesn't mean there won't be political disagreements.
Aside from operational cooperation, companies in both nations will be affected by the deals.
London and Paris agreed to fund assessment reports for a medium-altitude, long-endurance drone called MALE, with first products to be delivered between 2015 and 2020. They will also explore options on developing a joint fighter drone.
Britain's BAE Systems said it was in discussions with France's Dassault Aviation over cooperation on drone development, Defensenews.com reports.
France and Britain have laid out a 10-year strategic plan to enable efficiency savings in the complex weapons sector, which might lead to joint developments or even joint ventures.
Next year, the powers will launch joint projects to develop an anti-surface missile and assess where existing missile systems can be improved.
Potential additional cooperation could affect the nuclear submarine sector, training and spares support for the Airbus A400 military transport plane, satellite communications and naval mine countermeasure systems, Defensenews.com reports.
Eager to modernize its armed forces and rein in a massive national deficit, Britain recently announced it would cut defense spending by around 8 percent by 2015.
Even after the cuts, Britain and France will remain Europe's two largest military powers.