They were the single greatest collection of heroes of their time, bar none. Sure, there was the Liberty Legion, the Kid Commandos, and of course, the Crusaders, but no single group of costumed heroes are as well-remembered as the mighty Invaders. When they originally formed, the Invaders consisted of five powerful men without peer, including the following:
Bucky: Captain America's original partner, James 'Bucky' Barnes is a con man and swindler, and doesn't have any problem getting his hands dirty to get what he wants - and what he wants is to protect the world from the Nazi scourge! Availability:
Captain America: sole survivor of an experimental super soldier serum trial, sickly Steve Rogers quickly became a hero. Growing into his role as the Sentinel of Liberty, he gave his all in the fight against America's many, many foes! Availability:
the Human Torch: an artificial man created Phineas T. Horton, this android proved to be 'flawed' when he ignited upon exposure to air. Eventually mastering his powers, he took the name of the Human Torch, and used his abilities to fight evil! Availability:
Namor, the Sub-Mariner: son of an Atlantean princess and an American sea captain, Namor initially despised humanity. When he saw the worst of them in the form of Nazi Germany, Namor allied with humans of power like his to oppose their every move. Availability:
Toro: his parents being exposed to both asbestos and radium as youths, Thomas Raymond was born a mutant. He eventually developed powers like the Human Torch's, and the duo founded a crime-fighting partnership that lasted for years! Availability:
Shortly after their formation, the Invaders saw the addition of two more heroes to their fold, Spitfire and Union Jack. Both from England, these two were actually relatives, but gained their impressive powers under different conditions. Furthermore, towards the end of World War II, the team gained an all-new Captain America and Bucky when the originals were lost in the Arctic.
Bucky 2: after the first Captain America and Bucky seemingly perished at sea, the government quickly replaced them for the sake of public morale. Fred Davis, a friend of Bucky Barnes, was chosen to fill in for his lost buddy! Availability:
The Spirit of '76 / Captain America 3: the patriotic William Naslund became a costumed vigilante known as the Spirit of '76. After his hero's untimely demise, William was chosen by the United States government to fill Captain America's shoes! Availability:
Spitfire: given an emergency transfusion by the Human Torch after she was bitten by the vampiric Baron Blood, Lady Jacqueline Falsworth was forever changed, the two artificial influences within transforming her into the startling Spitfire! Availability:
Union Jack 2 / Mighty Destroyer 2: given a Super-Soldier Serum variant to keep it out of Nazi hands, British socialite Brian Falsworth broke out of the German prison holding him and used his new powers to combat the fascist scourge! Availability:
This collection of heroes worked well together, either all together or in smaller groups, despite their individual differences. You see, they intimately knew what their Nazi foes were capable of, and were able to put aside lesser concerns such as 'personality conflicts' for the greater good. They stuck together through thick and thin, until the very end of World War II.
Once the War was over and the Nazis were defeated, the membership shifted considerably, as did their mission. No longer having Nazis to contend with, they took on various other foes that solo heroes simply couldn't handle on their own. Furthermore, they took on a new identity, that of the All-Winners Squad. That team is covered more fully in its own entry, below.