In Damascus people call it the “million-dollar checkpoint,” although it is not one but two face-to-face roadblocks, barely a rifle shot apart. On a suburban road between government and opposition zones of control in Damascus, President Bashar al-Assad’s soldiers and their rebel enemies inspect cars, vans, and pedestrians. Their shared objective is extortion, exacting tolls on medicine, food, water, and cigarettes, as well as people, that are moving in and out of the besieged orchards and homesteads about ten miles from the center of Damascus in an area known as the Eastern Ghouta.

This devastated region, where a half-million people lived before the Syrian civil war, was the scene of the regime’s chemical weapons attacks in August 2013 that nearly drew American air power into the conflict. Partly as a result of a deal with Vladimir Putin, United Nations inspectors arrived instead, and removed or destroyed most of the government’s poison gas stocks. Since then, the frontier between the state and its opponents has provided profits to both. Such cooperation between enemies surprises those unfamiliar with Syria’s political and economic landscape, although neither side has concealed its recurrent contacts with the other.

The fierce game between the government and its adversaries is not confined to Eastern Ghouta. Wherever the warring sides want peace, there is peace. Where they contest territory, as they did until recently in the eastern quarters of Aleppo, there is war. Where they want profits, they collaborate. Hence, the “million-dollar checkpoint” and lesser checkpoints throughout the country that sustain the business of war. Paltry exactions from beleaguered citizens add up to large fortunes, giving the fighters incentives to mute the conflict in certain areas and marshal their forces elsewhere.

No one denies that the regime is winning the war. It owes its ascendancy as much to its opponents’ disunity and incompetence as to its own effectiveness. Rebel policy, whichever group was involved, was to seize and hold terrain for as long as possible in violation of every tenet of guerrilla warfare. The local people welcomed the rebels in some places and tolerated them in others.

In both cases, opposition fighters failed to shield people from the regime’s sieges and assaults as well as the misbehavior of their own “rogue elements.” Rather than wage a mobile guerrilla war and build a solid coalition within the population, they occupied land they could not hold. This alienated many Syrians whom the rebels could not govern and risked the lives of those they could not defend. The rebels failed to create effective alliances among their more than a thousand armed bands. Their reliance for arms and other support on rival outside powers—Turkey, Saudi Arabia, and Qatar, with the United States, Britain, and France in the wings—left the rebel groups vulnerable to the antagonistic and variable priorities of their sponsors. In sum, the opposition had no more chance against the Syrian regime than the similarly fractured Palestine Liberation Organization had in the 1970s and 1980s against Israel’s superior military and intelligence apparatus.

From the outset, forces loyal to President Assad held the main population centers, notably central Damascus, most of Aleppo, and the coastal cities of Tartous and Latakia. During the past year, the government, with Russian and Iranian assistance, recovered pieces of lost territory. While the battle for eastern Aleppo raged last autumn, parts of suburban Damascus were coming back under Assad’s control—discussions with the rebels were followed by capitulation.