Cyber security on warfare?

Hey everyone. I recently saw a Marines commercial on YouTube that captured the next era of warefare, being technology based.
I was curious with any wars previous/ ongoing wars, how has cyber security been involved in wars? Are there any weak points that nations go after? What are nations looking for in regards to cyber security? Are they using vulnerabilities to intercept messages? Are vulnerabilities being exploited in warfare that help enemy forces gain intel on their enemy through cybersecurity? …

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