Editor's note: Justin Bronk is a research analyst in the military sciences program at the Royal United Services Institute in London.Follow him on Twitter. The views expressed are solely those of the author.

(CNN) -- It is a question that the global community is seeking to understand as the crisis in Iraq and Syria deepens. How can such a numerically small force as ISIS, which calls itself the Islamic State, have taken control of vast swathes of Syria and Iraq, and how can it hold the ground taken while simultaneously conducting multiple offensive actions in both countries?

The most recent CIA estimate in September 2014 put the total number of ISIS fighters in Iraq and Syria at between 20,000 and 31,500. But such numbers, while alarming, are not nearly enough to explain the stunning military successes the group has enjoyed.

Justin Bronk

ISIS is at heart a guerrilla army that has recently captured large stocks of modern and heavy weaponry.

READ: Opinion: Will ISIS 'weaponize' foreign fighters?

While the equipment that makes headlines is war planes, captured tanks, heavy artillery and American-made Humvees, most ISIS fighters are still armed with the same mix of Soviet-era small arms and American M16/M4 pattern rifles that their Iraqi, Kurdish and Syrian opponents rely on.

Report: ISIS has 3 warplanes

Iraqi militias make small gains

ISIS pushed back in Kobani

Photos: The ISIS terror threat

Much of the heavy equipment ISIS has at its disposal was captured during their lightning advance into Iraq, not before. It is not the core reason for their battlefield successes. However, what it does do is make planning any battle against ISIS forces an uncertain exercise because one may have to face weapons and vehicles from right across the capability spectrum.

When it comes to offensives against prepared positions, ISIS forces can certainly deploy heavy artillery, modern weapons and tanks that give it greatly enhanced capabilities and completely outgun Kurdish Peshmerga forces in particular. Unconfirmed reports have suggested that ISIS even deployed a captured M1A1 Abrams in its takeover of the Mosul Dam, before eventually being driven back by repeated U.S. airstrikes.

This is where airpower can make a difference since heavy artillery, tanks and armoured vehicles are vulnerable to airstrikes when concentrated in the open such as at the Mosul Dam and in the current offensive to take Kobani.

What air power cannot do is easily degrade or neutralize ISIS's core advantages which are strong battlefield leadership, significant tactical autonomy and aggressive tactics. Their battlefield tactics are somewhat reminiscent of the German Blitzkrieg campaigns in the early part of World War II. They use fast, well-coordinated forces with vehicle support to attack enemy weak points in strength under the cover of long range artillery and mortar fire.

A particular speciality is outflanking defensive positions and then mopping up defenders who attempt to retreat. The tactic is as much psychological as it is kinetic, and is greatly magnified by the horrendous and public brutality ISIS has systematically exhibited wherever it has gained control.

從游擊隊到征服者：如何ISIS已經改變
由賈斯汀·布朗克，為美國有線電視新聞網
二○一四年十月一十八日 - 更新0858 GMT（1658 HKT）
賈斯汀·布朗克：ISIS的是，已經佔據較大的個股有現代武器的游擊隊。
賈斯汀·布朗克：ISIS的是，已經佔據較大的個股有現代武器的游擊隊。
新聞提要
賈斯汀·布朗克：ISIS戰機的數量還不足以說明該集團的成功
布朗克：大多數ISIS的戰士，手持蘇聯時代的小型武器，M16 / M4步槍圖案
ISIS使計劃對他們的不明朗任何戰鬥，寫布朗克
什麼空中力量不能做很容易降低或中和ISIS的核心優勢，他說：
編者按：賈斯汀·布朗克是一個研究分析師在英國皇家聯合服務研究所在倫敦的軍事科學計劃。按照他的Twitter上，發表的觀點僅代表作者本人。
（CNN） -這是一個問題，國際社會正在尋求了解在伊拉克和敘利亞危機的加深。試問，這樣一個數字小力的ISIS，其自稱為伊斯蘭國家，都採取了敘利亞和伊拉克的大片廣袤的控制，以及如何能保持地面拍攝的同時進行這兩個國家多次進攻行動？
最近美國中央情報局估計在2014年9月把ISIS戰機在伊拉克和敘利亞的總數在20,000和31,500。之間，但這樣的數字，而驚人的，幾乎沒有足夠的解釋令人驚嘆的戰績本集團享有。
賈斯汀·布朗克
賈斯汀·布朗克
ISIS是在心臟，最近拍攝的大量庫存和現代化重型武器的游擊隊。
閱讀：觀點：威爾ISIS的“武器化”的外國戰機？
而成為頭條新聞的裝備戰機，俘獲坦克，重砲和美國製造的悍馬，最ISIS戰機仍裝備有蘇聯時期的小武器和美國的M16 / M4模式相同的結構步槍，他們的伊拉克人，庫爾德人和敘利亞反對派依靠。
報告：ISIS有3架戰機 伊拉克武裝分子進行小的收益 ISIS推回Kobani
組圖：ISIS的恐怖威脅 組圖：ISIS的恐怖威脅
大部分的重型裝備ISIS在掌握了他們的閃電提前進入伊拉克時拍攝的，而不是之前。它不是最核心的原因為他們的戰場上的成功。然而，它要做的就是使規劃對ISIS的任何戰鬥迫使一個不確定的運動，因為一個可能要面對的武器和車輛從對面的能力範圍。
當談到對預備陣地進攻，ISIS的力量當然可以部署重砲，現代化的武器和坦克給它大大提高了能力，完全處於下風庫爾德準軍事部隊的力量尤其如此。未經證實的消息表明，即使是ISIS的部署捕獲的M1A1艾布拉姆斯在摩蘇爾水壩的收購，才最終被逼退美國多次空襲。
這是空中力量可以發揮作用，因為重砲，坦克和裝甲車輛很容易受到空襲時，集中在開，如在摩蘇爾水壩和在目前的進攻採取Kobani。
什麼空中力量不能做很容易降低或中和ISIS的核心優勢，有較強的戰場領導，顯著戰術的自主性和積極的戰術。他們的戰場戰術是有點讓人聯想到在二戰初期德軍閃電戰活動。他們利用快速，協調良好的力量與汽車的支持來攻擊敵人的薄弱點強度遠程火砲和迫擊砲火力的掩護下。
一個特別的專長是包抄的防禦陣地，然後掃蕩誰試圖以退為進的維護者。該策略是盡可能多的心理，因為它是動能，以及由可怕和公共殘暴的ISIS系統地展示地方才得到了控制，極大地放大了。