There are compelling political reasons why the Soviet Union, despite its probable need for new energy imports by the mid- 1980s, would not want to make a grab for the oil installations in southwestern Iran.
Thus, Soviet armed forces in Afghanistan do not appear to be driving toward a military takeover of Iran's oil fields, US intelligence analysts say.
The presumed Soviet goal of ultimate control over all the region's oil and natural gas (which the Russians already receive from both Afghanistan and Iran) might come, in the Kremlin's reasoning, after the internal political collapse of the central government in Tehran.
By playing on the tribal and ethnic nationalism of Pushtus, Baluchis, Kurds, and other Muslim peoples spread out around the flanks of the oil fields, these analysts say, the Soviets may try to so outflank Iran and so weaken it that not a single Soviet soldier will have to die there.
What is more, according to military-intelligence experts, the Soviets do not seem to be in a hurry about subduing the Afghan rebels with large-scale winter offensives. Their immediate military game, these experts say, is apparently to keep control of Afghanistan's few major cities and airfields, purge its puppet armed forces, and wait for better spring or summer weather to tackle the Muslim fighters in their mountain retreats.
The Soviets originally moved four motorized rifle divisions into Afghanistan by land and airlifted an additional reinforced airborne division of four regiments (instead of the usual three).
Two of the rifle divisions drove south from the Soviet border town of Kushka, near the northwest corner of Afghanistan. The other two crossed the border from Termez, on the Amu Darya River, about 200 miles farther east and headed for Kabul.
The two Kuskha divisions moved from Herat, the largest city in western Afghanistan, southward to secure the two key towns and air bases at Shindand and Kandahar. This brought the Soviets within tactical air range of the Gulf and the US Navy task force now in the Arabian Sea. But high mountain and desert barriers and poor or nonexistent roads rule out a land push toward the Iranian oil field from there.
In recent days, a fifth motorized rifle division of about 12,000 troops was withdrawn from the border with Iran east of the Caspian Sea. It moved by rail through the Soviet railjunction of Mary down into Afghanistan.
Soviet MVD and KGB internal security troops now are deployed as though to guard both main rail links through Soviet territory to the Afghan border. This suggests to some analysts that the Soviets fear guerrilla activity among some of their own Muslim people of the same ethnic and religious groups as those south of the border.
The Soviets have so far fought nothing but defensive battles, Pentagon analysts say. They have encountered rebel opposition in many areas, especially between Jalalabad and the main Khyber Pass route into Pakistan.
In the northeast, the Afghan Army -- suffering attrition from constant desertions and defections -- is being hard pressed by rebels at Feyzabad, the capital of Badakshan Province, not far from possible mountain supply routes from China.
The Soviets might eventually have to take over the job of defending or even recapturing Feyzabad. But they appear in no hurry either there or anywhere else , analysts say.
There main army headquarters at Kabul, given the new designation of "40th Soviet Army," is being duplicated by another western headquarters at Shindand, which the Russians apparently consider safer than the hostile larger city of Herat. Analysts expect permanent military division of the country between eastern and western commands.
Two squadrons of MIG-21 fighters and one of Sukhoi-17 attack planes; and 60 helicopters, including about 30 gunships (not enough for a large offensive) now are based in Afghanistan.The supersonic Soviet MIG-25 Foxbat fighter has made its first appearance in swift reconnaissance passes, but these planes, US analysts say, are based inside the Soviet Union.