It’s more complicated in a time of war and security in the presence of a state actor becomes much harder. Many messengers (e.g. WhatsApp) support e2e encryption. However, just having e2e encryption is not enough and there other things to be taken into consideration (ordered from more to less concerning from my pov):
1) The device will have unencrypted messages and keys. If device gets into wrong hands (e.g. owner gets killed or captured) then those can be read by an attacker. Even using disappearing messages might not help since OS can cache things or take screenshots saved somewhere (like iOS does).
2) Any group chat communications are increasingly less secure than 1-1 chats. There might be spies in the group or legitimate participants might get killed (see above). There is a trade off between efficiency and security.
3) The state actors might have ways to compromise devices through malware and get access to decrypted messages on the device through screen capture or directly in storage.
4) There might be unknown zero-day vulnerabilities exploited by state actors that are not known to developers of e2e encryption.
The bottom line is that e2e encryption is better than nothing but it does not offer 100% protection. As any other communication methods, there are inherent risks associated with distributing information to more people and these risks need to be taken into account.
1) The device will have unencrypted messages and keys. If device gets into wrong hands (e.g. owner gets killed or captured) then those can be read by an attacker. Even using disappearing messages might not help since OS can cache things or take screenshots saved somewhere (like iOS does).
2) Any group chat communications are increasingly less secure than 1-1 chats. There might be spies in the group or legitimate participants might get killed (see above). There is a trade off between efficiency and security.
3) The state actors might have ways to compromise devices through malware and get access to decrypted messages on the device through screen capture or directly in storage.
4) There might be unknown zero-day vulnerabilities exploited by state actors that are not known to developers of e2e encryption.
The bottom line is that e2e encryption is better than nothing but it does not offer 100% protection. As any other communication methods, there are inherent risks associated with distributing information to more people and these risks need to be taken into account.
Edit: typos