Compared to the United States, Russia's and Iran's air forces lack the ability to quickly locate and destroy targets -- which is critical for success in battle.

This process, commonly referred to as the "kill chain," is an enduring framework for delivering weapons on targets and can generally be broken down into specific steps: find, fix, track, target, engage and assess.

Success in modern warfare relies on a military's ability to take decisive combat action, such as dropping a laser-guided bomb to destroy an enemy missile launcher or jamming an adversary's radars.

Military forces have to find the targets, fix their position or track them, engage with precision and determine if they were successful.

Closing these chains is key to success.

Since the 1990s, the United States has taken numerous steps to speed up the closure of kill chains.

While reaction times for the US military in the 1991 Gulf War could last as long as one day, current kill chains take as little as minutes to close.

In the late 1990s, US Air Force Chief of Staff John Jumper challenged his force to reduce the time for striking an emerging threat to fewer than 10 minutes -- a timeline that seemed outlandish to skeptics at the time, according to a 2017 article by War on the Rocks.

Today, the US Air Force can routinely locate and destroy targets within minutes.

Kill chain failure

By contrast, the Russian air force has demonstrated major kill chain issues amid the Kremlin's invasion of Ukraine.

In Ukraine, Russia has relied on the Sukhoi (Su)-25 and Su-34 jets to hit tactical targets and close the kill chain with air power.

Both aircraft lack the advanced sensor suites of their Western counterparts that enable them to locate targets and close kill chains.

The Su-25 is designed for close air support and equipped with a heavily armored, composite metal airframe for withstanding damage from ground-based weapons, according to the National Interest.

The twin-engine, single-seat aircraft has eight pylons under its wings that can carry 4,000kg of air-to-ground weapons, including rockets, missiles and bombs.

While more recent versions of the Su-25 have modernized targeting, electronic warfare capabilities and navigation suites, they reportedly still lack a proper optical search device.

That weakness forces pilots to visually identify targets, slowing the kill chain process and forcing them to fly low.

It also makes the aircraft vulnerable to Ukrainian air defenses, including shoulder-fired weapons like the US-made Stinger.

The Su-34 "Fullback," a twin-engine, all weather supersonic medium-range strike aircraft, also suffers from limitations that affect Russia's kill chain.

The aircraft, which entered service with the Russian air force in 2014 and will eventually replace the Su-24, is designed primarily for tactical strikes against ground and naval targets on solo and group missions or for aerial reconnaissance.

The Su-34 is reportedly better equipped optically than the Su-25, but it has limited pilot viewing angles that hinder target identification.

It also lacks active electronically scanned array (AESA) radar, which has a longer range, higher ability to detect smaller targets and better resistance to jamming than does the Su-34's older passive electronically scanned array (PESA).

As of March, the Russian air force has lost 105 fixed-wing aircraft in the war against Ukraine, according to Oryx, an open source intelligence website that collects visual evidence of military equipment losses in Ukraine.

That includes 31 Su-25s, out of an original fleet of about 200, and 25 Su-34s, out of an original fleet of about 150.

Russia has also lost other aircraft key to the closing of kill chains -- namely, the two recently downed Beriev A-50 "Mainstay" airborne early warning and control (AEW&C) aircraft, a component crucial to the Russian air surveillance picture over Ukraine.

Implications for Iran

Iran, which relies on Russian-made aircraft, would likely face the same kill chain deficiencies in any potential conflict.

The Islamic Republic's air force has approximately two dozen Su-24s and 19 MiG-29s in service.

The aging Soviet MiG-29 Fulcrum acquired in the early 1990s was designed as an air defense fighter with dual-purpose ground attack capability.

Meanwhile, Iran has finalized plans to purchase Su-35 fighter jets, Mi-28 attack helicopters and Yak-130 jet trainers, Iranian Deputy Defense Minister Mehdi Farahi said in a statement in late November.

The deal reportedly includes two dozen Su-35s, but it is unclear when those will be delivered.

But even the Su-35 lacks key capabilities as the only major fourth-generation aircraft without the option of an AESA radar.

That means that other fourth-generation aircraft equipped with AESA radars are likely to be able to detect and engage an Su-35 beyond visual range before it can react.