FlaK!

Text by Tom Laemlein

The battle between the ground attack aircraft and the anti-aircraft gun proved to be one of the most important military microcosms of the 20^th Century.  Along the way, Germany’s quadruple 20mm AA gun, the 2 cm Flakvierling 38, became one of the iconic weapons of World War II. 

The origins of the 2 cm flak date back to World War One, as Germany produced the Becker 2 cm Type M2 autocannon.  The Becker would become the basis for the famous Oerlikon 20mm gun, one of the most effective and long-serving light AA guns of all time.  While Oerlikon produced their improved Becker design, Germany’s Rheinmetall sought to produce their own version of the 2 cm AA weapon, even though these were forbidden by the terms of the Treaty of Versailles.  Rheinmetall circumvented the legal logjam by selling the 2 cm “Flak 28” to Switzerland’s Solothurn (which was owned by Rheinmetall).  Solothurn proceeded to make a new 2 cm AA weapon called the ST-5, which leveraged the powerful 20x138mm round, sometimes called the “Long Solothurn”.  Eventually, the ST-5 became the Flak 30.

While the new Flak 30 autocannon was adaptable and powerful, the weapon suffered from a low cyclic rate (about 120 rounds per minute)—exacerbated by the gun’s small 20-round magazine capacity.  The problem of a low magazine capacity lingered, even as Rheinmetall improved the weapon with the Flak 38 (adopted by the Wehrmacht and Kriegsmarine in 1939).  Even though the Flak 38 was lighter in weight, and cycled at a respectable 220 rpm, the under-sized 20-round magazine remained in use throughout its service.

Even so, the Flak 30/38 offered additional uses—particularly as an anti-weapon during the 1930s and the early WWII era.  Basic armor-piercing ammunition (Panzergranatpatrone L’spur) for the 20x138mm round could penetrate 20mm of armor at 100 meters, and 15mm out to 500 meters.  The Solothurn ST-5/Flak 30 guns were credited with AFV kills during the Spanish Civil War (used by Nationalist forces) and during the Sino-Japanese War (used by Chinese forces).  During WWII, the Panzergranatpatrone 40 round was developed with a tungsten-carbide core and was capable of penetrating 39mm of armor at about 100 meters. 

Increased firepower to meet a growing aerial threat

By the end of the 1930s, aircraft were gaining speed and offensive capability.  Wehrmacht planners saw that their 2cm AA weapons, although capable, were in danger of being overwhelmed by a new generation of tactical bombers.  In fact, the Germans were already looking to move up to 37 mm guns—firing at about the same rate as the Flak 38 but delivering a punch many times more powerful at a much greater range.  While the Wehrmacht deployed a fair amount of 37mm AA guns by the end of the war, there were never enough to meet the demand.  Consequently, Rheinmetall introduced an upgraded variant of the Flak 38, the “2 cm Flakvierling 38”, mounting four barrels on a central rotating platform. The Flakvierling began to appear in service during late 1940.

Despite its powerful appearance, the Flakvierling was simply a coupling of four individual Flak 38 guns into one convenient spot.  The cannons do not fire any faster, nor do they have any other greater capabilities than a standard single-barrel Flak 38.  The quadruple grouping makes the individual barrels easier to load and puts their concentrated firepower under the control of a single gunner.  However, the same underlying shortcomings of the single-barrel Flak 38 still apply—particularly the low capacity of its 20-round magazine feed.