A day of battles

The 6th April seems to have been a day when battles took place.

• 46 BCE: The Battle of Thapsus: During the last of the Roman Civil Wars, veteran forces under the command of Julius Caesar defeated the forces of the Optimates (or Boni, a conservative republican faction) led by Quintus Caecilius Metellus Scipio at Thapsus in Tunisia. This defeat led to the suicides of Quintus Caecilius Metellus Scipio and Marcus Porcius Cato (Cato the Younger).
• 1812: The storming of Badajoz: Anglo-Portuguese forces under the command of General the Earl of Wellington (later Field Marshal the Duke of Wellington) assaulted the fortress of Badajoz, thus ending the almost month-long siege. 4,800 Allied soldiers were killed or wounded storming of the breaches, and for the following three days the survivors went on the rampage, looting and killing anyone who tried to resist them. They were eventually brought back under control after a number were flogged and a gallows was erected to hang anyone who failed to stop. The capture of Badajoz secured the Portuguese–Spanish frontier, and allowed Wellington to begin his advance into Spain.
• 1862: First day of the Battle of Shiloh: The Confederate Army of Mississippi (commanded by General Albert Sidney Johnston, with General P G T Beauregard as his second-in-command) launched a surprise attack on the Union Army of the Tennessee (commanded by Major General Ulysses S Grant) which was based at Pittsburg Landing. General Johnston was killed during the first day of the battle and late in the evening General Beauregard decided to defend the gains that the Confederates had made rather than continued the attack. On the next day, three divisions of the Union Army of the Ohio (led by Major General Don Carlos Buell) joined the Army of the Tennessee, which mounted a counter-attack, which cause the Confederates to retreat.
• 1865: The Battle of Sailor's (or Sayler's) Creek: This was the last major engagement between the Confederate Army of Northern Virginia (commanded by General Robert E Lee) and the Army of the Potomac (under the overall command of Union General-in-Chief Lieutenant General Ulysses S Grant) during the Appomattox Campaign. The Army of Northern Virginia surrendered three days after the battle ended.
  
• 1941: Operation 25: Following the Yugoslav coup d'état on 27th March 1941 which installed Peter II as King of Yugoslavia in place of the pro-German regent, Prince Paul, Hitler signed Führer Directive No.25, which ordered the German armed forces to invade the country. The invasion began with a massive air attack on Belgrade and the destruction of much of the Yugoslav Air Force. The Yougslav armed forces were unable to withstand the onslaught, and country was occupied by 18th April.
• 1941: Operation Marita: On the same day, Operation Marita, the German-led invasion of Greece, began. Although the Greeks and their British, Australian, and New Zealand allies fought hard to stop them, the Axis forces reached Athens on 27th April and the southern coast of Greece by 30th April. The 7,000 British, Australian, and New Zealand troops who were not able to be withdrawn were captured and the Greek armed force on the mainland surrendered. Crete was captured a month later, and Greece was occupied by German, Italian, and Bulgarian forces.