The Syrian Civil War may be the first known great power struggle of the post-9/11 world, in which the U.S., other world powerbrokers, and major regional players are fighting each other directly or by proxies. To America’s embarrassment, the biggest winners may be Russia and Iran. It may therefore be helpful for Washington to understand what strategies Moscow and Tehran rely on. Especially in cases of future civil wars that spiral into international conflicts.

Both Russia and Iran have managed to score major strategic victories in Syria for themselves and Syrian President Bashar al-Assad’s benefits in surprisingly low-cost ways. Consider Russia. Russia intervened on behalf of the Syrian government, but under limited measures. With memories of the Soviet war in Afghanistan still in the minds of the Russian public, Moscow’s official intervention has been manifested primarily as air support. Doing so has allowed Russia to save the Syrian regime from collapse, but without high costs or casualties. More interestingly, the Kremlin has increasingly relied on PMC’s as stand-ins for regular troops.

Aware of a potential negative reaction from the Russian public and lacking a local population that their troops could readily blend into as with the war in eastern Ukraine, Moscow has been hiring mercenaries to fight on Syrian soil. By utilizing contractors who take orders from Russian commanders, but who are technically not formal Russian soldiers, the Kremlin can deny any expansion of its commitment, and therefore avoid a public backlash fueled by fears of a military quagmire, but can conduct combined ground-air operations when necessary.

The Iranians also seemed to have found their own formula for success. Russia may be al-Assad’s greatest asset in the air, but Iran has supplied a bulk of necessary ground support for the Syrian regime in the forms of Hezbollah and, according to some reports, clandestine Iranian troops. Iran’s greatest contribution, however, may be in the thousands of Shiite volunteers fighting for al-Assad that Tehran has organized and transported en masse to Syria. These Shiite militias draw upon fighters with diverse ethnic backgrounds, such as Afghan Hazaras and Iraqi Arabs, and depend on Iran for the organizational and logistical capacity to operate in Syria.

The militias have performed remarkably well in campaigns such as Aleppo, and, most importantly, have allowed Iran to secure their influence in Syria. With Damascus having regained control of segments of the Iraqi-Syrian border, Tehran has reconstructed a “Shiite Crescent” stretching from eastern Iran to Hezbollah-controlled southern Lebanon. The militias present Iran the option of effective military interventions under the cover of plausible deniability of direct engagement and without having to pay for high Iranian casualties that would otherwise lower morale at home.

As Iran engages in a cold war struggle with other regional players for influence over the Middle East, we should expect Tehran to reuse Shiite militias as a strategic tool in areas with significant Shiite populations. Because so far, Iran’s experiment with militias comprised of foreign Shiites is working.

In retrospect, we shouldn’t be so surprised that the Syrian Civil War has become a great power struggle. The Spanish Civil War of the 1930’s, for example, likewise started as an internal conflict but expanded into a battlefield with foreign actors. Moreover, the war in Spain proved ample testing grounds for world and regional powers to practice new strategies and weaponry.

The Spanish Civil War, sometimes referred to as “Europe’s dress rehearsal,” marked one of the first usages of modern military aviation since World War I. The bombing of Guernica, immortalized by Picasso’s painting, showed that mass bombardments of civilian areas could produce significant strategic military advantages. Not long after, the Nazis would unleash the Blitz upon London, and the Allies would follow suit by heavily bombing Axis cities.

Mass bombings would continue after World War II, and the U.S. in particular would rely on its air superiority to incinerate urban areas in North Korea and North Vietnam. The war in Spain prompted the Soviets to send both material assistance and military advisors to Spanish communists, providing useful experience in proxy warfare years before the Cold War. Without getting directly involved, Moscow used Spain as an opportunity to attempt furthering its geopolitical agenda. The violence and chaos of the Spanish Civil War alone was tragedy significantly worsened by the involvement of outside players.

The civil war in Syria, like Spain before it, show us that conflicts started within failing states do not necessarily stay limited to domestic actors. Rather, they can become testing grounds for new military strategies and opportunities for global or neighboring great powers to expand their influence. Furthermore, as demonstrated by Russia and Iran, intervening powers can do so in relatively cheap ways. However, the dilemma of civil wars as potential international conflicts goes both ways for all actors.

If Russia and Iran can use another country’s internal conflict to their advantage, so can the U.S. and its allies. Adding to the insult would be if Washington decided to use Russia and Iran’s own tactics against them. Rather than full-scale military invasions like with Iraq in 2003, the U.S. could resort to low-key air interventions complemented with private military contractors and/or native militias on the ground. While doing so would be tantamount to a declaration of war if done inside of Russian and Iranian borders, Washington could plausibly do so in weak or failing states where Moscow and Tehran have high stakes and investments. Examples include Ukraine, Yemen, Tajikistan, Georgia, or Iraq.

With a Syrian government military victory looming on the horizon, American efforts in the Syrian Civil War may fail. However, if it has been an international standard to intervene in civil wars as far back as 1936 with Spanish Civil War, then it stands to reason that the U.S. could legitimately do so in any internal conflict. And as evidenced by Russia and Iran, there are ways to do so without committing significant blood, sweat, and money. Maybe it’s time for Moscow and Tehran to taste their own medicine.