The First and Second Battle of Tacna
As of the beginning of the third year of the war, Chile appeared victorious on all fronts. The Peru-Bolivian Army was in shambles, having totally collapsed in the Gran Chaco, losing huge swaths of territory to the surprise Ecuadorian entrance into the war, and having garrison after garrison surrender in the Atacama Desert. The Chilean military split into two camps - one of which favored a bold assault into Lima - the other which hoped to just seize the capital of Tacna and try to hold off any American reinforcements that would arrive to aid their beleaguered client state. At that point, it was seen as a huge mistake by the Americans to move the Peru-Bolivian capital to Tacna, because it meant that the Chileans didn't need to go very far to besiege the capital.
Landing north of the capital, the Chilean Army met the Peruvo-Bolivian Army in a notoriously one-sided confrontation. Corrupt American and Peruvo-Bolivian officers notoriously had sold off most of the shells for the Peruvo-Bolivian artillery - an early artillery duel devastated the Peruvo-Bolivian Army for hours before officers realized that most of the shells being launched at the Chileans were
duds. The Peruvo-Bolivian military had been trained essentially in the American method of war, as perfected in the World War I, which relied on powerful logistical and medical systems, which simply allowed the Americans to overwhelm their opponents with constant artillery barrages and mass infantry assaults. After all, despite being technologically inferior, fielding almost entirely untrained conscripts, and not actually enjoying any numerical superiority, the American Army had famously broken the British Army at the Battle of Toledo, in what was widely seen as a global humiliation to the British.
The problem with the American way of war was that it fundamentally did not work with a country with a relatively corrupt and low morale officer corps, and in a poorer country without a deep pool of institutional knowledge on how to run complex logistics systems. The British sarcastically replied that every third American was an entrepreneur who spent their free time memorizing roads and counting beans. That was not the case in Peru-Bolivia, and as a result, the PBC Army, severely degraded already by constant Chilean artillery, completely collapsed after a disastrous charge. Out of 19,000 Chilean soldiers that marched on Tacna, 37 died. Out of roughly 18,000 PBC soldiers, an estimated 4,000 died in combat, of their wounds, or of disease, with another 5,000 captured.
A panic quickly ensued in the capital. Much of the leadership of the Peru-Bolivia Confederation, which were essentially corrupt yesmen to the United States, fled the capital with whatever valuables they could carry. Furious Peruvians attacked government officials as they fled. The situation would essentially be salvaged by a relatively low-ranked bureaucrat by the name of Guillermo Billinghurst, who led a small group of technocrats in organizing a civil defense of the city. Simply handing out guns to everyone who would take one and building barricades on every street, the provisional Peruvo-Bolivian government was determined to defend Tacna to the end. Although the Americans were scared of simply arming everyone, the situation was grave enough so Billinghurst's plan was approved. Chilean attempts to breach the city simply resulted in horrific losses on both sides, as superior Chilean artillery simply meant that Peruvian militias could fight in the rubble.
Given the terrible sanitary situation in Tacna - and the general belief that Chile needed to preserve its troops if American reinforcements showed up, it was decided to simply siege the city and allow it to starve. As a result, rampant disease raged across Tacna, killing tens of thousands. However, the city simply refused to surrender even as the death toll piled up - largely because it was quite easy for the leadership to hold out hope for American reinforcements. A set of large fortifications were dug around the city and also along the coasts, in preparation for an American landing.
The landing would eventually come - and unlike the first Battle of Tacna, the American way of war would actually at least partially work. Neither the Chilean Navy nor the American Pacific Fleet was actually eager to get into a pitched confrontation. The Americans were afraid severe navy losses would destroy their entire influence network on the Pacific Coast, while the Chileans feared that navy losses would jeopardize the largely successful Argentine front. The Chilean Navy was largely happy interdicting American shipping to make it harder for the Americans to resupply, largely evading American patrols.
American troops landing were able to engage Chilean fortifications, though most of the engagements were essentially bloody messes for both sides. Smart observers realized that the method of warfare in Tacna would be quickly mirrored in the future - the futility of Americans bombing and charging Chilean fixed fortifications - and then being forced out again by an equally costly Chilean counterattack meant almost no movement over months. Both sides would continually funneling reinforcements into the meat grinder. Over several months, the Tacna campaign would essentially see around 11,500 Chileans and Americans each killed (with significantly higher American wounded totals). In practice, the Americans took significantly higher casualties, but superior American medical care managed to keep deaths lower than expected.
Ultimately, the campaign would end in an Axis victory, as the Chileans simply took too many losses to maintain their siege of Tacna, even in spite of the constant reinforcements. Peruvo-Bolivian militia guerillas quickly filtered out of the city and began harassing Chilean supply lines, driving their logistic situation to a crisis. Realizing that the Chilean Army could not hold, a decision was made to retreat them back to Chile proper. The fear was that cut off from Chile proper by the Atacama Desert, the entire Chilean Army could be destroyed. In the last days of the campaign, the Chileans would make a dramatic evacuation. As far as evacuations went, it was largely seen as largely successful, except around 600 Chilean soldiers who stayed behind to help the others retreat (and were eventually killed or forced to surrender). Ironically, where Peru-Bolivian garrisons littered the Atacama, now Chilean garrisons littered the desert, hoping to inflict losses severe enough on the Americans to exit the war with control over the Atacama. Of course, the human costs in Tacna were beyond hideous, with Peru-Bolivia also needing now to draw manpower essentially far away from the front.
Going into the 1908 Presidential elections, the Beveridge Administration celebrated what appeared like a great victory - or at least a "turning point." However, their detractors pointed out that not only were American losses rather heavy, but that they hadn't actually managed to win the war. The Argentine front was still seen as an abject disaster, Ecuadorian forces were still occupying large swaths of northern Peru-Bolivia, and Brazil continued to appear like a hopeless morass, with Americans dying in mass numbers from ambushes and disease (the actual primary killer in the Brazil front for both sides).