The North Atlantic Treaty Organization (NATO), created in 1949 to contain and deter Soviet aggression, has been the most successful defensive military alliance in history. Through forty years of Cold War, military planning focused on preventing and blocking a Soviet military assault across the north German plain while reinforcing the so-called northern and southern flanks of the alliance immediately adjacent to Russia and her Warsaw Pact allies. The "flanks" and the "underbelly" were always of concern because they were the most distant and therefore logistically difficult to reach.

Now, a quarter of a century after the Berlin Wall came down and the Soviet Union disintegrated, NATO faces a new weakest flank and softest underbelly. Both have become exposed and made far more vulnerable by the Russian annexation of Crimea and more dangerously, by events in Syria and Iraq. There the Islamic State of Iraq and Syria, ISIS or ISIL for the Levant as it is now known, has established temporary sovereignty across a considerable landmass in that region under the strictest reading of Sharia law.

The new "caliphate," as its leaders call it, is dedicated to Jihad and spreading the most perverted forms of Islam -- so violent that ISIS has been repudiated and rejected by al-Qaida! The combination of Russian occupation of Crimea and Islamist-Jihadi violence and terrorism has profound consequences for the West and indeed for Russia as well. It is these consequences that form the greatest new dangers and threats to NATO's exposed flank and soft underbelly.

Vladimir Putin has relied on the tactics of an earlier Vladimir -- V.I. Lenin -- in seizing control of Russia and advancing the influence of the Communist Party. The use of paramilitary forces; intimidation and blackmail; propaganda; cyber; and agents in place whether operatives in deep cover or dissatisfied minorities are part of this modus operandi. As far back as 1924, Lenin attempted to annex Estonia using these methods and failed.

Similarly, ISIS multiplies the effectiveness of these tools through extreme uses of violence and terror. Iraq is a bit different however because ISIS has been able to rally, manipulate and attract large numbers of discontent Sunnis angry with the Shia-led regime in Baghdad and what Donald Rumsfeld famously called "dead-enders," survivors from Saddam Hussein's rule and his Sunni army. Also in play are hundreds if not thousands of Western insurgents with valid passports learning the terrorist trade. The argument and fear is that many of these Islamists will return to their homelands ready to wage Jihad.

That NATO is a military alliance has meant that its strength has rested in its nuclear and conventional military forces. Unfortunately as should have been learned in Afghanistan, the real dangers today do not arise from only military threats. Unconventional or nonconventional actions from terrorism and cyber to disruption of ways of life are the new exposed flanks and soft underbellies to be protected.

For over a decade, a series of Supreme Allied Commanders Europe had begged, cajoled and warned the alliance of the need to deal with these and other new dangers. Cyber, energy security, protection of vital infrastructure, preventing disruption of society and countering terror have been high on the agenda for action. However, the need for consensus, meaning unanimity, among 28 different and sovereign states and very different perceptions of threat and means to deal with that have not made strengthening this new vulnerable flank easy.

The forthcoming biennial summit of heads of state and government in Wales in September is an ideal opportunity to address this huge gap and vulnerability in alliance thinking, planning and capability. Nearly fifty years ago, NATO was at a similar crossroads. The strategy of nuclear deterrence and retaliation was being challenged by Soviet improvements in conventional forces where NATO was at a large disadvantage. A study was commissioned that became the famous Harmel Report, named for the chairman and former Belgian prime minister.

The report produced the strategy of "flexible response." Flexible response was a brilliant political solution. The allies pledged to spend more on conventional defense that placated the Americans (although they never spent what the U.S. demanded) and the U.S. restated its commitment to defend Europe with nuclear weapons if needed. Both sides of the Atlantic got what they wanted.

Today, NATO needs a new Harmel Report. The principal danger is not enemy armies, navies and air forces. It is a combination of intimidation, terror, propaganda and political strategies to subvert. These are the new vulnerable flanks and soft underbellies. And they must be fixed.

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Harlan Ullman is Chairman of the Killowen Group that advises leaders of government and business, Senior Advisor at Washington D.C.'s Atlantic Council. This column comes from his latest book, due out this Fall, is A Handful of Bullets: How the Murder of Archduke Franz Ferdinand Still Menaces The Peace.