Outside the new NATO headquarters in Brussels, two memorials stand vigil: a fragment of the Berlin Wall facing a twisted piece of metal from the Twin Towers. Both are silent reminders of the importance of investing in collective defense to protect our security, freedom and democracy.

For nearly 70 years, NATO has helped keep the peace in Europe by investing in defense and deterrence.

Boosting allied defense investment has been one of my top priorities since becoming secretary general in 2014. That year, NATO allies agreed at our Wales Summit to stop the cuts, gradually increase defense spending and move toward spending 2 percent of their gross domestic product on defense by 2024. In 2017, we estimate a real defense spending increase of 4.3 percent in Europe and Canada — a third straight year of accelerating increases. This translates into an additional $46 billion in spending over the past three years. Along with five other allies, Romania has announced the intention to reach 2 percent in 2017, and Latvia and Lithuania have indicated they will do the same in 2018.

So while we still have a long way to go, we are going into the right direction.

Early next year, allies will report on their specific defense investment plans, covering three main areas: cash, capabilities and contributions. In other words, how they will meet their commitment to spend 2 percent of GDP on defense; how they will invest additional funding in key military capabilities; and how they will contribute to NATO missions and operations.

This increased investment in defense will set the scene for our summit in Brussels next July, where we will have the opportunity to review the progress we have made in implementing the most substantial increase in our collective defense in a generation. We are already working on several key areas where NATO must continue to adapt. We will also decide on the next steps to respond to evolving security threats.

First, we will finalize plans to update our military command structure — the backbone of our alliance. A robust and agile command structure underpins both our strengthened deterrence and defense posture as well as our ability to project stability beyond NATO’s borders. One new element we envisage is the creation of a new cyber operations center to strengthen our cyber defenses and integrate cyber capabilities into NATO planning and operations at all levels. A new command for the Atlantic is planned to ensure sea lanes of communication between Europe and North America remain open and secure — so crucial for transatlantic coordination and mutual defense. We also plan to create a new command focused on military mobility — to speed up the movement of military forces and equipment within Europe.

Military mobility is key to effective and credible collective defense. NATO has been working on this for several years to remove legal hindrances to crossing borders. But we also need to address infrastructure requirements — military-grade roads, bridges, railroads, tunnels, ports and airfields — and optimum means of transportation. This requires close cooperation with national governments and with the European Union. I expect military mobility to become a flagship achievement for enhanced NATO-EU cooperation.

Meanwhile, the EU’s role in European defense is set to increase. I welcome the launch of the Permanent Structured Cooperation, in which 23 EU member states agreed to cooperate on defense and security policy. This has the potential to help drive increased defense spending, provide new capabilities and improve burden-sharing within the alliance. But we need to keep in mind three points to ensure that NATO and EU defense efforts are complementary.

First, we need coherence when it comes to development of capabilities. We must avoid the same nations having two sets of requirements for the kind of capabilities they should develop. Second, we need to be sure that European forces and capabilities are also available to NATO to avoid competition. And third, we need the fullest possible involvement of non-EU NATO allies in the consultations and in the process. This is critical because, after Brexit, 80 percent of NATO defense spending will come from non-EU allies, and three of the NATO battlegroups deployed to Eastern Europe will be led by non-EU allies.

NATO and the EU have achieved a great deal since signing our joint declaration on NATO-EU cooperation at the Warsaw Summit. We are already implementing a wide range of measures across many areas, including maritime, exercises, defense industry and research, defense capabilities, and hybrid and cyber defense measures. In 2018, we will continue to explore what more we can do together, in particular to support the fight against terrorism.

On the ground, NATO is ramping up its efforts to provide training and assistance to Iraq in multiple areas, including counter-improvised explosive devices and demining, military medicine, and reform of the country’s security institutions. In 2017, we launched an in-country training initiative, deploying a team to Baghdad to facilitate NATO’s training and capacity-building programs to support Iraq’s fight against terrorism and instability. This effort will grow in 2018.

Our mission in Afghanistan remains NATO’s largest. And we have agreed to increase its size from around 13,000 to 16,000 in the coming months. Our troops are there to train, advise and assist Afghan security forces, to help them fight international terrorism, including ISIL, and to stabilize their own country. Our decades of experience, from the Balkans to Afghanistan, have taught us that one of our best weapons in the generational fight against terrorism is training local forces and building the capacity of local institutions. And this will remain a focus for us in the next year.

NATO is the most successful alliance in history because it has adapted as the world has changed. As we continue to adapt in 2018, NATO allies are committed to spending more and better on defense, improving burden-sharing among allies, strengthening our transatlantic bond and preserving the peace for future generations.

Jens Stoltenberg is the secretary general of NATO.