The Washington argument over which NATO members count as 'model allies' and which belong on some informal naughty list is a question about what the post-1945 arrangement was actually for. The standard story treats it as a favor the United States did for Europe. The more accurate story is that the United States built a structure for its own quieter benefit and let the benefits flow outward. Robert Kagan's short 2018 essay, The Jungle Grows Back, makes the second case as cleanly as anyone has, and it has aged into something useful for the 2026 debate precisely because it predates the names currently attached to it. You don't have to share Kagan's politics to find the essay clarifying. You only have to be curious about why a transactional approach to alliances tends to produce results its champions did not advertise.
Alliance debates are hard because the costs of maintenance are visible and the costs of withdrawal are not. Bases, exercises, basing-rights negotiations, and the irritations of dealing with smaller partners who freeride or grandstand all show up in budgets and headlines. The wars that didn't happen, the coups that didn't escalate, the trade routes that stayed boring, none of those generate invoices. So the political incentive to rediscover skepticism about NATO every decade or so is structural, not personal to any one administration. Most current coverage skips a serious account of what the suppressed alternative looks like once the suppression stops. That's the gap Kagan tries to fill, and it's why his essay reads less like a 2018 artifact than like a memo someone left on the desk for later.
Kagan's organizing claim sits in the title. He treats the relatively peaceful, rules-bound international order of the past seven decades as a cleared patch of ground, not a permanent feature of geography. Left alone, the older patterns return: great-power rivalry, regional wars, predatory regimes, collapsing rules. American power, in his telling, was the gardener, and the garden was always more fragile than its inhabitants liked to admit. The argument moves quickly through the postwar record because Kagan is not trying to write a history. He's trying to make a causal point.
The suppression of European great-power war, the integration of Germany and Japan into a system rather than against it, the slow expansion of democratic governance, none of these were inevitable consequences of trade or modernity. They required a guarantor willing to absorb costs that looked, from inside the system, like generosity and, from outside, like dominance. Kagan is fairly honest about that double face. He doesn't pretend American leadership was clean.
The essay sharpens in its treatment of 'realism.' Kagan argues that the version currently fashionable in Washington, the kind that frames allies as freeloaders and retrenchment as maturity, mistakes exhaustion for insight. Pulling back, in his account, doesn't produce a stable multipolar equilibrium. It produces the conditions great powers historically exploited, and then the United States gets dragged back in on worse terms. The deterrence argument is the load-bearing one here, and it's where the essay is strongest. It's also where you can push back, and I think you should. Kagan's framing has a tidiness problem. His central image implies that whatever isn't liberal order is reversion, which flattens a lot of variation in how regional powers actually behave when American attention drifts. China in 2026 is not the Kaiser's Germany, and treating every challenge as the same recurring weed undersells the specific strategic puzzles each one poses. The essay is also light on the question of whether the order's domestic beneficiaries have done enough to make its costs politically survivable at home, which is the actual reason the naughty-list framing has traction now. That's a real omission, not a quibble. Still, the essay does something most current commentary doesn't. It makes the cost of withdrawal concrete instead of rhetorical. It treats burden-sharing as a real grievance with a real answer rather than a slogan to be either endorsed or dismissed. And it's short enough that you can finish it in an evening and argue with it the next morning, which is more than can be said for most foreign-policy books that try to do similar work at three times the length.
If you read The Jungle Grows Back this winter, the question to carry into the rest of 2026 isn't whether Kagan is right about every case. It's whether the political coalition inside the United States that once made his argument routine still exists, and what fills the space if it doesn't. The essay was written before the current round of the debate and will outlast it. That's a decent reason to spend an evening with it, especially if your instinct is to disagree.