When shipments of weapons are captured crossing the Syrian border Turkish and Jordanian police often find amphetamines ("speed") pills as well guns and ammo. Turns out that the rebels consider speed an essential drug for their fighters. Amphetamines have long been used by military personnel to remain alert during combat situations. The Syrian rebels don’t have access to military grade amphetamine pills but instead rely on a commercial product; Captagon. This is the trade name for fenethylline, a synthetic drug that has the same effects as amphetamine but with fewer bad side effects (like increased blood pressure). Fenethylline was still pretty potent and by the 1980s most countries had either outlawed it or made it a prescription drug. Now the most common form of fenethylline is Captagon, which is widely available in the Middle East. Captagon is considered a major problem in the Middle East because there is so much illegal use of it. It is the stimulant of choice among many Syrian rebels as well as pro-government forces.
In the grand scheme of things Captagon is simply the latest mood control drug used by combat troops and its not the only one. For example U.S. Navy SEALs often use of sleeping pills (Ambien) while getting ready for operations. That often involves first flying long distances in cargo aircraft, then keeping odd hours in crude accommodations as final preparations are made. All this is quite stressful, making it difficult to fall asleep, even when exhausted. Getting some sleep is essential, so the SEALS are encouraged to take stuff like Ambien if they need it. Many journalists found this shocking. Some even found it disturbing. But taking sleeping pills and stimulants is an ancient tradition. The alternative is getting killed in combat.
The big problem is maintaining alertness in a stressful environment. Once in combat American troops are issued stimulant pills and gum to help them stay alert. Back in 2007 the U.S. Army began issuing "Stay Alert" caffeine gum to combat troops. This was yet another in a long line of drugs troops have been given to keep them alert after long hours in a combat zone. This fatigue problem has existed for a long time and has become particularly acute in the last century or so, as battles became endurance contests, with forces engaged for days on end.
The air force has a similar problem. In the last few decades, as long range bombers and refueling in the air became common, pilots have had to face alertness problems during very long (30 hours or more) missions. In sixty years of using "go pills" (amphetamines), the air force has never had an instance where the stimulant caused a crash or accident. In contrast, over a hundred crashes have been caused by pilot fatigue.
For over a century now one of the more popular fatigue solutions has been amphetamines. However, this drug can impair judgment, making the user more aggressive. Ambien has similar side effects. After September 11, 2001 kinder and gentler alertness medications became available. The most effective of these has been Modafinil (sold as Provigil). This stuff is described as "a mood-brightening and memory-enhancing psychostimulant which enhances wakefulness and vigilance." Tests showed that user performance was degraded 15-30 percent, versus 60-100 percent for those who took nothing at all after 24 hours of being awake.
While the Modafinil did a pretty good job, the dextroamphetamine was still a bit better. So amphetamines remained competitive. Another new stimulant, touted as superior to dextroamphetamine and Modafinil, CX717, was tested by the Department of Defense and found not appreciably superior to existing stimulants. Meanwhile, the U.S. Navy continues to use coffee, and lots of it, to keep sailors on their toes during long hours of continuous duty. But for infantry and pilots, a hot mug of coffee is often not an option.
Wakefulness can be a potent weapon, especially for commandos or troops engaged in prolonged combat (like the Battle of Fallujah in 2004). Without these wakefulness drugs you would have to either pull troops out of action so they could rest or leave them in and risk having them make fatal mistakes. Either way you have a problem because there are never enough troops to get the job done. But with the wakefulness medications you can solve the problem, for a few days, anyway.
Prolonged use of these drugs is not healthy. But neither is being drowsy during combat. It's better to get some sleep when you can, even if you have to take more medications to help make that happen. Troops exposed to prolonged combat find the stimulants lifesavers and consider them as essential as ammunition. Thus the Syrian rebels consider a weapons and ammo shipment incomplete if some Captagon was not included.