What I love most is the consistency of GW's vision. See this excerpt from page 39, the start of the article:
"Chapter Ultra-Marine of the Legiones Astartes was founded during the inter-legionary wars of the thirty second millennium. Tradition places the date at 4001001.M32 - the very first day of the millennium. The chapter is therefore over eight thousand years old, making it a chapter of the third founding. Upon its inception, the Emperor have the chapter the number 13 - formerly the number of one of the treacher-legions now banished to the Eye of Terror...the new chapter received the gene-sperm, implant zygotes, rituals, and other paraphernalia of indoctrination previously entrusted to the banished 13th legion. The chapter's founder was Roboute Gulliman whose bones now lie in the Reclusiam on Macragge."
Originally a fleet-based Chapter, they distinguished themselves in the First Tyrannic War (M34) and have fought in every one since, including the most recent (745.M41) after which they were awarded the water-based planet Macragge for their travails.
As now, the Ultramarines are led by none other than
Imperial Commander Adeptus Marneus Calgar, the fourth Lord Macragge. Following a skirmish against Hive-fleet 'Perseus' in 976, Calgar lost all four limbs as well as large areas of body tissue and his left eye. Now fitted with bionic replacements, he is more machine than man.
Since his injuries though, Calgar is no longer ever the field commander of the Ultramarines. :(
He has rules, of course, as you may wish to engineer a situation in which he is called upon to fight - but he doesn't even wear powered armour anymore as a general rule. Luckily he has a Conversion Field.
I bet you're wondering how Calgar came to rise to his position in his original fluff? Well, it may interest you to know that :
Calgar was amongst human prisoners rescued from Hive-fleet 'Locust' in the year 947 of the current millennium. His age was then estimated at 14...and was recruited into the order as a neophyte in the armoury. Calgar took his vows in 951 and was fully ordained as a brother marine in 954. He quickly rose through the ranks and was elected Master of the Household in 973 and Commander in 977 following the death of Decon, the Third Lord Macragge.
Like I said, fluff = awesome.
PS - Tyranids were believed to be the servants of Chaos.