What were the first two ironclad ships to battle in the civil war?

Explanation:

The Merrimack (aka the Virginia)  was the Confederate ironclad that threatened the Union's naval blockade.  The Merrimack (as it was originally named) had been a conventional steam frigate.  The South had salvaged the ship and renamed it the Virginia.  The upper hull was cut away and then covered in iron armor.  

The Monitor was the Union's ironclad ship built in response to the Confederate's ironclad.

The two fought each other at the Battle of Hampton Roads, (March 9, 1862), in the harbor at the mouth of the James River.  The outcome of battle between the two ironclads was not decisive for either side -- but did issue in a new era in naval warfare.

the berlin blockade was an international crisis that arose from an attempt by the soviet union, in 1948–49, to force the western allied powers (the united states, the united kingdom, and france) to abandon their post-world war ii jurisdictions in west berlin. in march 1948 the allied powers decided to unite their different occupation zones of germany into a single economic unit. in protest, the soviet representative withdrew from the allied control council. coincident with the introduction of a new deutsche mark in west berlin (as throughout west germany), which the soviets regarded as a violation of agreements with the allies, the soviet occupation forces in eastern germany began a blockade of all rail, road, and water communications between berlin and the west. on june 24 the soviets announced that the four-power administration of berlin had ceased and that the allies no longer had any rights there.