This year's biggest air battles are showing the US what it could need most in a missile war with China

• From Ukraine to the Middle East, air-defense systems have been put under immense stress this year.
• These big engagements show why it's important for militaries to have a strong air-defense network.
• They also offer the US military valuable lessons for a potential war with China in the Pacific.

Air-defense systems have been tested in unprecedented ways in conflicts around the world by global military powers and smaller militant forces alike.