Exercise Joint Warrior hit its halfway point over the weekend, and shows no sign of letting up. Plenty of challenges, from mine countermeasures to subhunting and amphibious assault, still lay ahead for the NATO and allied ships in one of Europe’s largest military exercises, led by the United Kingdom. And they’re not the only ones paying attention. News reports say a number of Russian ships have taken position on the periphery, and military inspectors from Moscow are keeping close watch. And with good reason: NATO nations have touted this as a show of strength to deter Russian aggression, and there has been plenty of…