Battle of the St. Lawrence

After his epic march through the Maine wilderness Arnold arrives on the St. Lawrence only to be confronted by the frigate HMS Lizard and sloop-of-war HMS Hunter. Arnold knows he could bypass them but he also knows that these ships could cause great difficulty in operations on the St. Lawrence.

POD Arnold decides to take the warships. Organizing two boarding parties and constructing canoe he catches the Lizard's crew unawares and seizes the ships the Hunter puts up more of a fight but is soon forced to surrender when faced with the Lizard.

In OTL Marines and sailors from both ships aided in the defense of Quebec on Dec. 31st and a carronade from Lizard was used to stop the southern American force(and killed Montgomery). The American attack goes the same way in OTL excepting that Montgomery isn't killed and Morgan isn't captured.

Over the winter in addition to the Lizard and Hunter, Arnold builds a number of row galleys at Sorel and Montreal, and transports the sloop Enterprise and several captured schooners from Lake Champlain to the St. Lawrence.

April 1776 A RN squadron consisting of HMS Isis a fourth rated frigate accompanied by two smaller frigates of under the command of captain Charles Douglas attempts too break through the ice laden St. Lawrence and relieve Quebec. Early on the 26th a look out sights the American squadron moving into a sheltered harbor.

Looking over the rebel ships Captain Douglas decides too move in for what he believes to be an easy victory. Arnold seeing that Douglas has taken the bait prepares his men for the coming action. Arnold has equipped his ships entirely with carronades and positioned his fleet in a protected harbor so that the enemy will have close in to engage his ships at close range. He has also positioned his fleet close enough to the shore that he can mount his entire armament too face the enemy.

The battle begins about mid day with the British closing in and delivering massive broadsides into the American squadron but Arnold's preparations bear fruit and the rebel carronades quickly even the odds. Both fleets are battered throughout the day, however Captain Douglas realizes that his position if untenable his ships are dismasted and smashed strikes his colors. Upon hearing the news of Arnold's victory Governor Carleton surrenders Quebec to Montgomery.

Thougths
 
Why would he surrender Quebec when everyone knew that British reinforcements (~4000 men) were on the way down the St. Lawrence just as soon as the ice cleared? If they survived as long as April then they could certainly survive a few more weeks.
 
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