Editing Battle of the Atlantic (section)

==British situation==
The German occupation of Norway in April 1940, the rapid conquest of the [[Low Countries]] and France in May and June, and the Italian entry into the war on the Axis side in June transformed the war at sea in general and the Atlantic campaign in particular in three main ways:
* Britain lost its biggest ally. In 1940, the French Navy was the fourth largest in the world. Only a handful of French ships joined the [[Free French Forces]] and fought against Germany, though these were later joined by a few Canadian [[destroyer]]s. With the French fleet removed from the campaign, the Royal Navy was stretched even further. Italy's declaration of war meant that Britain also had to reinforce the [[Mediterranean Fleet (Royal Navy)|Mediterranean Fleet]] and establish a new group at [[Gibraltar]], known as [[Force H]], to replace the French fleet in the Western Mediterranean.<ref>{{Cite journal |last=Simpson |first=Michael |date=1997 |title=FORCE H AND BRITISH STRATEGY IN THE WESTERN MEDITERRANEAN 1939–42 |url=http://www.tandfonline.com/doi/abs/10.1080/00253359.1997.10656629 |journal=The Mariner's Mirror |language=en |volume=83 |issue=1 |pages=62–75 |doi=10.1080/00253359.1997.10656629 |issn=0025-3359}}</ref>
* The U-boats gained direct access to the Atlantic. Since the [[English Channel]] was relatively shallow, and was partially blocked with minefields by mid-1940, U-boats were ordered not to negotiate it and instead travel around the British Isles to reach the most profitable spot to hunt ships. The German bases in France at [[Brest, France|Brest]], [[Lorient]], and [[La Pallice]] (near [[La Rochelle]]), were about {{convert|450|miles|km}} closer to the Atlantic than the bases on the [[North Sea]]. This greatly improved the situation for U-boats in the Atlantic, enabling them to attack convoys further west and letting them spend longer on patrol, doubling the effective size of the U-boat force. The Germans later built huge fortified concrete [[submarine pen]]s for the U-boats in the French Atlantic bases, which were impervious to Allied bombing until mid-1944 when the [[Tallboy (bomb)|Tallboy bomb]] became available. From early July, U-boats returned to the new French bases when they had completed their Atlantic patrols, with {{GS|U-30|1936|2}} docking at Lorient as the first arrival.{{sfn|Hellwinkel|2014|p=36}}
* British destroyers were diverted from the Atlantic. The [[Norwegian campaign]] and the [[Fall Gelb|German invasion of the Low Countries]] and France imposed a heavy strain on the Royal Navy's destroyer flotillas. Many older destroyers were withdrawn from convoy routes to support the Norwegian campaign in April and May and then diverted to the English Channel to support the withdrawal from Dunkirk. By mid-1940, Britain faced a serious threat of invasion. Many destroyers were held in the Channel, ready to repel a German invasion. They suffered heavily under air attack by the {{lang|de|Luftwaffe}}{{'s}} {{lang|de|[[Fliegerführer Atlantik]]}}. Seven destroyers were lost in the Norwegian campaign, another six in the [[Battle of Dunkirk]] and a further&nbsp;10 in the Channel and North Sea between May and July, many to air attack because they lacked an adequate anti-aircraft armament.{{Efn|Between April and July 1940, the Royal Navy lost 24&nbsp;destroyers, the Royal Canadian Navy one.}} Dozens of others were damaged.

[[File:Lorient submarine base 2007 2.jpg|thumb|upright=1.5|German [[Lorient Submarine Base|submarine pens in Lorient]], Brittany]]

The completion of Hitler's campaign in Western Europe meant U-boats withdrawn from the Atlantic for the Norwegian campaign now returned to the war on trade. So at the very time the number of U-boats on patrol in the Atlantic began to increase, the number of escorts available for the convoys was greatly reduced.<ref>[http://www.history.ca/ontv/titledetails.aspx?titleid=248473 Convoy] {{webarchive|url=https://web.archive.org/web/20110719201429/http://www.history.ca/ontv/titledetails.aspx?titleid=248473 |date=19 July 2011 }} from History Television.</ref>  The only consolation for the British was that the large merchant fleets of occupied countries like Norway and the Netherlands came under British control. After the German occupation of Denmark and Norway, Britain [[Invasion of Iceland|occupied Iceland]] and the [[British occupation of the Faroe Islands|Faroe Islands]], establishing bases there and preventing a German takeover.

It was in these circumstances that Winston Churchill, who had become [[Prime Minister of the United Kingdom|Prime Minister]] on 10 May 1940, first wrote to [[President of the United States|President]] [[Franklin Roosevelt]] to request the loan of fifty obsolescent US Navy destroyers. This eventually led to the "[[Destroyers for Bases Agreement]]" (effectively a sale but portrayed as a loan for political reasons), which operated in exchange for 99-year leases on certain British bases in [[Dominion of Newfoundland|Newfoundland]], [[Bermuda]] and the [[West Indies]], a financially advantageous bargain for the United States but militarily beneficial for Britain, since it effectively freed up British military assets to return to Europe. A significant percentage of the US population opposed entering the war, and some American politicians (including the US Ambassador to Britain, [[Joseph P. Kennedy]]) believed that Britain and its allies might lose. The first of these destroyers were only taken over by their British and Canadian crews in September, and all needed to be rearmed and fitted with ASDIC.<!--rather than US-spec sonar, that is... --> It was to be many months before these ships contributed to the campaign.