Ukraine fortifies air defenses amid tensions with Russia over missile strikes.

Ukraine is building a three-layered air defense network with a range of sophisticated Western systems to counter Russian air attacks. Russia has increased strikes in May, aimed at depleting air defense stocks so that fewer systems can be used to protect troops. The Avenger air defense system, supplied by the US, is an important part of the short-range end of the three-layered system. The system is highly mobile and effective near the battlefield, but there are too few of the systems to go around. Ukraine is pressing Australia to supply four-wheel-drive Hawkei vehicles that can be mounted with air defenses and used in the same way as Avengers.