European countries have committed to spending nearly double on military investments over the next decade, with high hopes that it will benefit their defense industries.

But it is not clear that all that money — perhaps as much as 14 trillion euros, or $16 trillion — will fuel a flurry of high-end innovation in Europe. That is because of what one might call the F-35 problem.

Europe lacks quality alternatives to some of the most needed and desired defense equipment that American companies produce. Among them is the F-35, Lockheed Martin’s famed stealth fighter jet, whose advanced abilities are unmatched by European counterparts.

Patriot missile-defense systems are also imported from America, as are rocket launchers, sophisticated drones, long-range artillery guided by satellite, integrated command and control systems, electronic and cyber warfare capabilities — along with most of the software required to run them.

And because many European nations have already invested in American weapons, they want new purchases to remain compatible.

The pledged investments have created a tension. Should European nations build their own military industry? Does the war in Ukraine and the threat of a militarized Russia allow that much lead-time? Or should they continue to invest, at least in part, in America’s already available, cutting-edge technology?