Strategy Page charts the increasing pace of change to the US army’s combat headgear:
Since 2000 combat helmet design has made enormous advances. The new helmets have increased protection (often against rifle bullets as employed by snipers) while becoming more comfortable to wear, more accommodating of accessories (especially personal radios and night vision gear) without becoming heavier. Combat helmets were long considered low-tech but that has changed since the 1980s. Creation of new materials plus advances in the design and construction of helmets have been accelerating, especially in the last decade. For example, the American ACH (Advanced Combat Helmet), as popular as it was after appearing in the 1990s, soon underwent tweaks to make it more stable. That was required because more troops were being equipped with a flip down (over one eye) transparent computer screen. The device is close to the eye, so it looks like a laptop computer display to the soldier and can display maps, orders, troop locations, or whatever. If the helmet jumps around too much it’s difficult for the solider to make out what’s on the display. This can be dangerous in combat.
The first modern combat helmets appeared during World War I (1914-18), with the U.S. adopting the flat, British design steel model and using it for 25 years. This was replaced by the M1 helmet in the early 1940s. This was the “steel pot” and liner system that lasted over four decades. The PASGT (Personnel Armor System for Ground Troops) replaced the M1 in the early 1980s and lasted twenty years. The ACH replaced PASGT by 2007 but by 2012 the ECH (Enhanced Combat Helmet) began appearing as a replacement. ECH, like ACH is built to take lots of accessories and is the version bought by police and emergency service organizations.
It was only in 2005 that the ACH began entering service. The Kevlar PASGT design was a third generation combat helmet, nicknamed the “Fritz” after its resemblance to the German helmets used in both World Wars. That German World War I design, which was based on an analysis of where troops were being hit by fragments and bullets in combat, was the most successful combat helmet in both world wars. This basic design was finally adopted by most other nations after the American PASGT helmet appeared in the 1980s. Most of the second generation helmets, which appeared largely during World War II, were similar to the old American M1 design. The fourth generation helmets, currently in service, use better synthetic materials and more comfortable design.