Also included were four rows of rivets on plating where stress would be greatest, and huge davits that could lower a lifeboat on the the other side of the ship if necessary. The last change was her name. She was originally to be called Gigantic, but White Star reconsidered after the Titanic disaster. These changes made her the largest in gross tonnage. As a hospital ship she was 5% larger, but as a commercial liner she probably would have been 10% larger than her older sisters. After the Titanic disaster, White Star seemed to become obsessed with safety.
The Britannic was launched on February 26th 1914, and White Star planned to steam her between Southampton and New York, starting in the spring of 1915. However, after the outbreak of World War I, she was to become a hospital ship. Some of her nearly complete interiors were stripped down, and her lounges and dining saloons became operating rooms, and dormitories.
The Britannic had a medical staff of 52 officers, 101 nurses, 336 orderlies, and a crew of 675 men and women. On December 12th 1915 she was commissioned His Majesty's Hospital Ship (HMHS), and she left Liverpool on December 23rd 1915. Her maiden voyage, to Mudros, on the isle of Lemnos.
During the Britannic's 5th voyage she encountered serious weather. She finally made it to port, but the Aquitania had been damaged in the same storm. The Britannic was forced to begin her 6th voyage to take the Aquitania's place, after only 4 days in port.
The Britannic left Southampton on Sunday November 12th, 1916. She was supposed to leave at 10:00AM, but ended up leaving at noon. The weather was calm, and she didn't carry any passengers. 
Friday November 17th, 1916 she arrived at Naples for coaling and was to depart on Saturday, but a harsh storm blew in and delayed the departure.
On Tuesday November 21st, 1916 the Britannic's "passengers" couldn't have hoped for better weather. Just as all were sitting down to breakfast, around 8:12AM, there was a tremendous noise from the starboard bow, and the entire ship trembled from bow to stern. Survivors said that it was much like the shock waves from an earthquake. You could feel the vibration moving, from the bow, to the stern.
The HMHS Britannic had struck a mine, and yet another "unsinkable" White Star giant was about to founder. The explosion damaged the watertight bulkhead between holds 2 and 3, and the bulkhead separating holds 2 and 1 was also "injured.' At the same time, boiler rooms 5 and 6 began taking water. This is roughly the same damage the TITANIC suffered (5 of the TITANIC's compartments were dammaged, and 6 of the Britannic's were, however since the Britannic had the added safety features, -in a sense- about 5 compartments had been damaged).
Two lifeboats were launched without permission just as Captain Bartlett ordered the engines ALL AHEAD FULL. He planned to beach the ship off the coast of an island that was only two miles away, Kea. (pronounced kay-a) However, one of the two lifeboats that were launched was sucked into the Britannic's still spinning propellers. Everyone jumped from the lifeboat, and it was pulled under, and crushed by the propellers.
One of the nurses in that lifeboat was Nurse Violet Jessop. She was aboard every one of the Olympic Class Liners when they were damaged. She was on the RMS TITANIC when she sank, she was on the RMS Olympic when the HMS Hawke rammed into her, and now she was going to survive yet another maritime disaster, this time on the HMHS Britannic. When she jumped out of the lifeboat, she hit her head on the bottom of the other. Luckily somebody pulled her in. As if Violet Jessop surviving three White Star mishaps wasn't odd enough, only years later did she discover she had fractured her skull when she hit the bottom of the lifeboat.
Enough about Nurse Violet Jessop, back to the sinking. The Britannic sank in only about 300ft of water. Now let's remember that she was 882.5ft long, just like her two sisters. Because of this, her bow was being crunched on the bottom, as her stern was getting a breath of fresh air 600ft above the surface!
The HMHS Britannic sank 55 minutes after the collision, and her "passengers" were saved by the resue vessel. It's amazing. Even with all of her added safety features, and similair damage to the TITANIC's, she sank in less than an hour. It's probabaly because there were open portholes that let water pour in after she sank down enough. Also, when Captain Bartlett tried to beach the ship, it just forced more water into the hull. The good side of it though, is that only 30/1200 people died, almost all of which were in the smashed lifeboat.
Of all the ships of the Edwardian era, the Britannic is one my favourites.
