WASHINGTON — When Gen. Philip Breedlove took over as the head of US European Command and supreme allied commander for NATO in 2013, the role was a relatively quiet one.

But as he handed over command to Gen. Curtis Scaparrotti this week, Europe is a very different place, one facing the three-headed challenge of Russian aggression in the east, terrorism threats from the south, and a migrant crisis which threatens to overwhelm the NATO member states.

Breedlove was a respected figure among NATO allies, with Adam Thomson, UK permanent representative to NATO, telling Defense News that Breedlove did a "great job" in the role.

"[Breedlove] has provided both intellectual and, if you like, moral leadership for the alliance as it responds to a fast-changing-threat picture, and we will miss him," Thomson said.

With a major NATO summit in Warsaw roughly two months away, Scaparrotti has little time to enjoy a learning curve as he moves to Europe after three years in South Korea.

While Thomson declined to give advice for Scaparrotti, analysts believe Breedlove provides a good template for his replacement going forward.

Gary Schmitt of the American Enterprise Institute thinks the best thing Scaparrotti can do to start is to follow in Breedlove's footsteps.

"There is a tendency in NATO to make lemonade out of lemons by accepting current limitations in budgets and capabilities and hoping that incremental improvements such as the new rapid reaction force is more than incremental," Schmitt said. "Scaparrotti has to avoid that tendency and, like Breedlove, he needs to keep publicly stating the nature of the threat posed by the Russian military and be clear about the shortfalls in the alliance to meet that threat."

Schmitt also said that, like Breedlove, Scaparrotti must maintain pressure on the NATO members and make sure they understand "that the alliance strategy of trying to get by with as little as possible in upping deterrence is high risk" in light of Russia's military buildup.

Jerry Hendrix, senior fellow with the Center for a New American Security, specifically called out Breedlove's attempts to increase the authorities of the supreme allied commander as a key initiative that Scaparrotti must continue so that the command "has more ability to move quickly during the embryonic stages of crisis rather than having to wait for those crises to be fully developed before the alliance can act."

He also noted that Scaparrotti "has to become a forceful advocate for the individual NATO nations to meet, at the minimum, investments in their own defense," which underlines the political nature of the role.

And that is where Breedlove was so strong, said Jeff Rathke, senior fellow at the Center for Strategic and International Studies. The outgoing commander used his presence and public remarks "extremely well" to keep public attention on the changed security environment in Europe and the need for NATO to change its response for modern times.

"You have now a political consensus in favor of strengthened defense among allies, and the US needs to remain engaged at this time to ensure that momentum continues," Rathke said. "We turned a corner and we need to keep the engagement up to ensure that allies meet their commitments.

A further area the new EUCOM head will have to focus on, Rathke said, is guiding NATO nations' procurement plans as they come out of Afghanistan. For 10 years, those nations have been focusing on buying expeditionary equipment; now they will be looking a more defensive gear.

"There is a refocus, a retooling, that has started and what NATO needs is to have the readiness and the ability to engage in territorial defense without losing the ability to engage in expeditionary operations," he said. "So the pendulum is moving back, but it shouldn't be rebalanced all the way toward territorial defense only."

Twitter: @AaronMehta