An example of a strong military ally is the United States of America and the Republic of the Philippines, they both agreed to sign the mutual defense treaty which states that both nations ought to support each other if either country were to be attacked by an external power. In the treaty itself it states that they are "Desiring to declare publicly and formally their sense of unity and their common determination to defend themselves against external armed attack, so that no potential aggressor could be under the illusion that either of them stands alone in the Pacific Area," the two countries have promised to provide for each other in the case of an external attack, meaning in the case of an attack either country will not have to stand alone but will have their ally to assist them. There are many military alliances existent today such as the Unites States and Japan, France and Germany and the European Union, who all aid for one another in times of need. Forming military alliances can be especially beneficial to the less equipped countries if they sign treaties with stronger and more powerful countries, as some are not well prepared for an external military intrusion. .
Being in a military alliance with another country definitely has its assets, however it also has its drawbacks as well. Partnering up with another country means you are obligated to follow whatever military decisions they make as well even though it is at your inconvenience, and can result in great alliance wars. An infamous example of how the alliance system had caused a detrimental outcome is the world war one; countries were hauled into the war by their alliances resulting in a massive world war. Germany was brought into the war by its ally Austria-Hungary and ended up being declaring war on Russia and being of the Central Powers that resulted in an ultimate loss. There are also the chances of your country acquiring more enemies, as it is likely that all your alliances enemies will become your enemies as well.
