Since 1949, North Atlantic Treaty Organization (NATO) was formed for the collective defense of its member states to respond to an attack by any external party.
NATO has a Standardization Agreement (STANAG) with member nations defining the processes, procedures, terms, and conditions for common military standards between members of the alliance. Each NATO state ratifies a STANAG and implements it within their own military.
The purpose is to provide common interoperability providing member nations structured communication and the use of another member's military material to enable more effective combined operations. STANAGs are published in English and French and there are hundreds of standing agreements. Here are ten of interest:
STANAG 2003: Patrol Reports
STANAG 2014: Operations Plans, Warning Orders, and Administrative/Logistics Orders
STANAG 2019: NATO Joint Military Symbology - NATO Military Symbols for Land Based Systems
STANAG 2310: 7.62×51mm NATO standard infantry rifle cartridge
STANAG 2868: Land Force Tactical Doctrine (ATP-35)
STANAG 2961: Classes of Supply of NATO Land Forces
STANAG 3680: NATO Glossary of Terms and Definitions (AAP-6)
STANAG 4090: 9x19mm NATO standard small arms ammunition
STANAG 4172: 5.56×45mm the standard for all NATO service rifles