John Chipman, director-general and chief executive of the International Institute for Strategic Studies, has written an article arguing that Iran has tipped the balance of effective force in the Middle East to its advantage.

“Iran has tipped the balance of effective force in the Middle East to its advantage by developing a sovereign capability to conduct warfare through third parties,” he wrote in an article published by The Telegraph on Thursday.

According to the BBC, Iran's regional rivals have spent billions of dollars on Western weaponry, much of it from the UK. 

Yet for a fraction of that cost, sanctions-bound Iran has been able to successfully embed itself across the region into a position of strategic advantage.
It has a major influence - verging on a controlling influence in some cases - over the affairs of Syria, Lebanon, Iraq and Yemen.

Iran has also developed unconventional forms of asymmetric warfare - such as swarm tactics and drone attacks - that have allowed Iran to offset its enemies' superiority in conventional weapons.
Following is an excerpt of the article:

In July 2019 President Donald Trump tweeted that “Iran has never won a war but never lost a negotiation”. The International Institute for Strategic Studies’ (IISS) analysis of Iran’s networks in the Middle East published today suggests a reversal: Tehran has lost faith in negotiations following the collapse of the Iran nuclear deal but has found a way to win in war.

While the conventional military balance remains in favor of the U.S. and its allies, Iran has tipped the balance of effective force in the Middle East to its advantage by developing a sovereign capability to conduct warfare through third parties. Iran avoids symmetrical state-on-state conflict. Instead, it pursues asymmetrical warfare through non-state partners. 

This sovereign capability is of greater strategic value to Tehran than its conventional forces, its ballistic missiles or even its rejuvenating nuclear program. It is a weapon of choice that is peculiarly suited to today’s regional conflicts. These contests are not defined by state-on-state warfare, involving parity of forces subject to international law, but are complex and congested battlespaces involving no rule of law or accountability, low visibility, and multiple players who represent a mosaic of local and regional interests.

Its doctrine is rooted in Iranian war-fighting experience and revolutionary ideology.